There are many different makes and sizes of electronic keyboard, each with different features. Ideally, 5 octaves and 61 full sized keys is a good size keyboard for a beginner and the minimum requirement to fully benefit from the pieces in Keysurfers, would be 49 full sized keys and 4 octaves.
It is important to have an auto-accompaniment button so that, whilst playing the tunes with the right hand, you can add left hand single finger or full chords, which control the backing beat.
Some suitable beginner keyboards, reasonably priced, are the Yamaha PSR series, for example:
It is useful to have an adjustable keyboard stand, as this can then be set up at the correct height for the student. It does not encourage correct hand position and comfortable posture if the keyboard is positioned regularly on the floor or a table.