Where can I take my FIL?

Hello y'all. I've been in Houston my whole life so I don't know the fun places to go, especially for an older person who's not going to do too much walking. I'm working most days he's here. I have one weekday to take him anywhere. I don't want it to be too expensive because I also have other guests that will be coming along. He's coming from Africa and I want to take him somewhere that he'll enjoy. He's about 70, mobile but not fit.