The aquarium and rain forest are amazing. Expect a full day to see everything. Its located right next to the Galveston Airport (walking distance). The whole family has made multiple trips to Moody Gardens.
Natalie and Dennis ran their first running race there together. Dennis had a awesome time there in his first 10k.
October is (surprisingly) the best time to go be in Galveston! The temperature isn't sweltering and the water is still warm.
You won't have a problem with Houston this one. The Johnson Space Center is a breath taking facility.
Crocodile Encounter is right past MSR Houston Race Track. Dennis owns a small business on the track that manages and repairs race cars.