Kids Fitbit/activity tracker watches

I brought my oldest who’s 10 a Fitbit for Xmas, he loves it and now our younger son wants one for his 5th bday next month. But sadly the Fitbit ace 2 is to big for his wrist. So I’m looking for something similar that would fit a younger child. I’ve looked at vtech, leapfrog and Garmin watches. They all look good but some reviews for vtech & leapfrog aren’t that great. Garmin one seems the better choice. But wondering if I’m missing another brand that’s just as good as the more expensive ones? I’m in the U.K. so need to be available here. Thanks 😊