Kids don't like warm baths when the weather is hot, of course, they want a cold bath to refresh themselves. This is same goes with us. I think they will prefer warm bath or the mixture of hot and cold. Did you already tried it? Hot bad is irritable but it can loosen up some stress in their body and for sure, even if they perspire, all the hot feeling, the pain in the muscle and of course, stress will all be gone. I remember my nephew, he was bathe with warm water. He felt sleepy after because he felt tired already because of the hot bath experience. When he is bathe with cold water he is playful. Maybe that is their complains or problem. Better to ask your kids of what is the real problems and you go in the middle to solve this problem.