Things to do for visitors?

Just found out that I have a couple friends visiting Houston tomorrow. I’ve lived here for over a decade but I’m not very outgoing myself so I don’t know what’s worth doing here. I know that I wanna take them to the galleria and also to visit my uni (UH) and possibly Rice as well (they’re into that sort of thing). Anything else? What’s a good Christmas-y thing to do (daytime only, they’re leaving by 6pm)?