I have actually stayed at the Trident (when I could use Hilton points) and walked to the Udaivillas for dinner one night. I would say that the kids, and there for the parents, would probably have a better time at Trident. You don't mention the ages but the kids could be kids at the Trident pool. I did an inspection of Udaivillas and while it was a beautiful property for adults I don't think it would be that great for the kids.
I really liked the Trident. The staff were wonderful.
The outdoor restaurant at the Udaivillas is gorgeous, especially at night, with a full moon.