I used rollers in the '70s and then trainer stands for many years, but now I prefer exercise bikes---I can get as hard or easy a workout as I like, and I can save my bikes for outdoor use. It might take up a little less space than a bike on a trainer stand; plus, older riders are likely to appreciate the more upright sitting position.

Just make sure that you like the saddle or that the seatpost has a conventional clamp so that you can replace the saddle if desired.