It should be fine as long as you make sure there is a protective cover over the filter - keep the temp within "reasonable" range: my parents have a hot tub that the little ones love to go in with the adults. There is a federally approved safety cover for the filter (one proven that it will keep hair and body parts from being sucked into the filter which is a HUGE problem causing many many drowning deaths nowadays) and we keep it about 98F when the kids will be going in it. I mean, you put your child in a hot bathtub every day, its not the temp of the water that is the concern.
Toddlers have sensitive skin though - all I watch out for is a rash from the chemicals. We use bromine as opposed to chlorine, it is more gentle on the skin. Have fun!