You have said you live 2 hours from a place where a DP could be repaired, and you are very concerned about reliability and after-sale service (now about sound).
There's a lot to read in the forum, but perhaps the first thing is to change your attitude. You don't like your Casio, and you didn't make a good purchase. Ok, then try to learn some lesson from it all that help you in the future.
How about negotiating some (3 year?) home assistance with the dealer (perhaps at the cost of some extra money), like an insurance?
And with regards to the sound...nothing better than a live test.
Yamaha: round, stretched, well built, old technology, reliable. Your daught, you and grandma will al like it!
Kawai: bright, dynamic, risky, innovative, more character, hard to drive.
Software pianos: I guess it should be your choice. Better overall sound (and more customizable), you can choose every component in the sound chain (good 2nd hand options) and get spare parts when needed...this, along with maybe some sertraline would do it easier, from my own experience