I am answering about the kids question. I put my tub down to about 99 deg for my 5 and 6 year old granddaughters but you will find that most kids are not like adults. They don't sit still and most times they are only waist deep. They treat it more like a warm pool then a hot tub.
As to the other question 102 all year round.
Thats a good point! I try to tell shoppers this when they are trying to find a spa that has a seat for 6' dad, 5'6" mom and little Johnnie and Suzie.
As there kids are climbing in and out of one spa after another I say:
"See what the kids are doing now? Thats what they are going to do in the spa in your back yard. They will use you as an obstacle corse and climb around from seat to seat. They aren't going to sit until they are 12-14, earlier if its a girl."