I believe that the Blue Bell factory is only open on weekdays. That catches a lot of people by surprise.
The 6th Floor Museum is pretty impressive. I feel extremely emotional when I'm there. Expect it to be fairly busy.
My favorite thing in Austin is the capitol building. It's pretty impressive. The Austin area is lovely with hill country nearby and lots of wonderful little towns. It's hard to tour those though.
As for hotels, do you prefer historic or resort or chains? There are a lot of options.
DH is very excited about the 6th floor museum so that's good to hear! I would love to explore Hill country more, but that'll be another trip when the kids are older or when it's just DH and me. As for hotels, I personally prefer historic/charm, but I think priority needs to be proximity to sites and nice pools or other entertainment for the kids... would also love them to be easy on the budget of course, but we can pay a bit more if it's great ammenities for the kids.