Funny that you mention switching from the Inset to the Cleo because I recently did the opposite! I never had a problem with the cleo falling out, but hte adhesive always seemed to leave behind much more band-aid-like goo than my Inset does. The main reason I switched is because I am a wus when it comes to inserting my infusion sets, and with the Cleo you have to be brave and just punch it down. I always ended up inserting it slowly, which hurt more. With the Inset I can be a baby all I want, and when I finally get the courage to press the little buttons it does the work for me, quick and painless.
If you’re inserting the sites for your son, or even if he is doing them himself, being able to insert the Cleo’s quickly enough might be a factor to consider (band-aid goo definitely being lower on the list).