Did a family road trip this summer and stopped at Hot Springs as an overnight stopping point. One bathhouse allows 10 and up and I think the others are 14 and up. Ours is under ten so we did the Observation Tower (big tower on the towns high point) it was neat enough but nothing too cool.
We did the Alligator farm which I highly recommend for an 8 & 12 year old boy. It's a classic old private roadside alligator zoo. Our 5 year old got to feed little alligators, hold a little alligator and feed big alligators too, but sense your going at Christmas all the alligators will be inside.
https://alligatorfarmzoo.com/Overall, with an 8 year old, you can't go to any of the bathhouses, which is what all the tourism is built around.