I love your 'trial run' idea. Because some will embrace and love it, others, not so much.
I do agree with people about including a stylus. Old arthtritic fingers might appreciate a finer touch. I'd say also a larger, chunkier case. Protect it from drops and give them something larger to hold onto.
As to apps, e-readers, solitaire, help loading family photos. Perhaps help setting up facetime or a chat program with family members. i have a mahjong game that I like to play. maybe hook the senior up to family facebook pages, etc.
Of course, the student teachers can help the seniors find their way around the app store and load it with what they like.