Piano vs. Electronic Keyboard
For that matter you can get an electronic Piano.
One of the "key" differences is the weighting of the keys. With pianos, you have weighted keys so as you feel resistance when pressing a key you create a certain volume. The harder you strike the key, the harder the felt covered hammers in the mechanical part of the piano strike the strings which then vibrate to produce the tone.
Keyboards also mimick this feature with different levels of dynamics, but unless it is a weighted keyboard the playing is unnatural. IMAO you should learn on a weighted keyboard. If you can, get an acoustic upright piano and that can always be in the central part of your home to beckon reluctant learners to sit down and play, plus they can "perform" for guests and family at home.
Later you will probably add to the collection anyway and get a portable keyboard that you can take to other band members places or go to perform with, but for songwriting and learning the piano, nothing beats the action of a real piano.