I can promise you at least a portion of bites come from "puppy dog tame" monitors. Mood swings are real, accidents can happen. I personally think it's a horrible idea to mix children and something that can cause horrendous damage in the blink of an eye.
https://www.google.com/search?q=moni...bites&tbm=isch
I think you should build the adult enclosure first if you decide to get one. If you provide for it right you'll be needing that enclosure sooner than you probably think anyway.