Very seldom does is sprinkle. It either pours buckets or doesn't bother.
BTW, TX Rowing Center, just west of your route, rents recreational (wide) rowing shells suitable for someone who gets out very occasionalluy. Also kayaks and SUPs. It's easy to go out for an hour on the river. II don't know if this would be back friendly for you though.
Have a good visit.
A row seems like it would be really fun, but not sure my back would like it.
If you haven't been to the Umlauf Sculpture Garden before, I can recommend it. We visited when Max was ~5 and they had a fun seek & find thing for the kids -- almost like sculpture orienteering. But the sculptures and grounds are interesting even without that.