Welcome
Whilst I may be making a lot of assumptions it does seem as though you both may want very different keyboards.
I would say that your Wife could be up and playing Pop music pretty quickly with an Arranger keyboard, now depending upon price Yamaha PSR E463 > Casio CT X5000 > Korg PA700 > Korg PA4X.
As for yourself, research MIDI, there are masses of songs in the MIDI format that you can download and play.
DAW software such as the free Cakewalk by BandLab will get you going and a MIDI controller keyboard as per those listed below.
Above all please do not rush it, learning to play takes a lot of practice time, effort and reading theory books.
Following is a series of basic notes that might help to clarify some confusion.
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Do you want to play a Piano or Keyboard?
That is the question my Teacher asked when I took up playing keys after years with a guitar and bass.
He qualified it by stating, there is a difference in how I teach you and in how you will develop.
Piano.
At its most basic level LH plays the Bass lines and chords, RH plays the melody.
Independent LH & RH playing actions will need to be developed.
A Digital Piano is just that 88 weighted keys with a variety of Piano sounds to call upon to be used, other sounds can also be incorporated within the unit.
Keyboard.
Two basic types, Workstation and Arranger.
Both start with 61 keys and as the models increase in complexity and cost 76 key and 88 keys versions become available as budget increases.
Each type of unit has hundreds if not thousands if instrument sounds that can be used as an example there can easily be over thirty different types of Piano sounds available to be selected.
Workstation.
Highly customisable, often with inbuilt recording, looping, and the ability to set sequence patterns of sounds that can be called upon at the touch of a button.
Usually over one thousand instrument sounds available to be used.
Orchestral sounds can be built up by layering one instrument on top of another to produce a Combination that can be saved into a User area and assigned to a Favourite button.
Watch a Band and the person on keys will probably be playing a Workstation, if they have more than one unit then a digital Piano is likely to be there unless your name is Rick Wakeman then the number of keyboards he uses is often in excess of ten.
Arranger.
A keyboard that typically incorporates onboard amplification and speakers for a fully self contained unit.
Instrument sounds or voices are categorised into families with typically thirty specific instrument sounds available.
These keyboards include Auto Accompanying of styles that are or can be triggered by the left hand.
The keyboard is electronically split (adjustable and can be switched off) so the Accompanying sounds are played with the LH and RH plays, melody lines, arpeggiated chords, improvisation, melody accompanying lines, syncopations etc.
A beginner to keyboards will probably start off learning on a low value Yamaha or Casio unit and then progress to more complex keyboard.
Synthesizer.
Is an electronic sound generator, it can be a keyboard or non keyboard model.
With all the above keyboard types, there is a considerable degrees of overlap and incorporation of functions within each category.
The choice of which type will be best for you is dependent upon what you want to play, the style and long term plans.
If you have doubts or just want to dip ones toes in then an Arranger will probably be the best unit to go for. With the auto accompaniment feature it will enable you to produce music relatively quickly.
Technicals
Polophony, this is the number of different instrument sounds that a keyboard can play at the same time.
Styles, there are hundreds of presets arrangements including in an Arranger keyboard, each Style will have a specific number of musical instrument sounds included and when the Style is initiated it will provide sounds and rhythm related to a music genre like dance, r n b, waltz, rock, ballad etc
Songs, some keyboards have a specific style, rhythm and instrument sounds that are intended to produce a sound similar to a popular song such as Ed Sheeran’s Thinking out loud, John Lennon’s Imagine, Elvis Presley The Wonder of You, Glenn Miller Moonlight Serenade etc songs that span many decades of music to cater for all ages.
Sustain pedal, a foot operated on/off switch that if it is pressed and held as a key or keys are pressed the note(s) continue to sound until the pedal is released.
Recording
Most keyboards have the ability to record your performance, the degree of flexibility and editing capabilities does vary substantially. That said a substantial number can be connected to a PC/MAC where audio recording software can record your performance but taking recording to another level is software known as a DAW where you can create a multi layered track, each with full individual recording and editing capabilities, many good DAWs are freeware.
Virtual Instruments
A MIDI keyboard controller, DAW software and a whole series of software instrument sounds can give a very capable Recording Studio in its own right. This setup can also provide a very economical entry into keyboard playing for the computer literate.
General advice
Keyboard manufacturers have online manuals available to download for current and older keyboards therefore it can be useful to read said manual to help gain an understanding of a specific keyboards features.
Keyboard manufacturers also have Video Tutorials online which can give a good grounding on the features and on using a specific keyboard.
Online reviews vary from excellent to dire so do take them with a pinch of salt, if any start with, wassup, then move on to another video.
Be flexible in your choices as what you think will be the best keyboard for you does not necessarily relate that it is the one for you.
Do not get hung up on a particular manufacturers products.
Yamaha produce some excellent keyboards but they produce very cheap ones to get learners locked into the brand, but their tutorials and customer support are almost non existent. Their higher end learner keyboards and their top of the range Arranger are the standards others have to match or better.
Within a specific price band the capabilities of different manufacturers products are very similar.
Keyboards to consider
Beginner/improver keyboard
Yamaha PSR E series
Roland Gokeys/Gopiano
Arranger
Korg PA700/1000
Roland EA7
Korg PA4X
Yamaha Genos
Workstation/Synth
Korg Kross 2
Roland Juno DS61
Workstation
Roland FA 06
Korg Kronos
MIDI controller keyboards
Novation Launchkey
Arturia Keylab Essential
Native Instrument Komplete Kontrol