I find it to be incredibly selfish to enter your child in two brackets at the same tournament. I've seen more than once where a child has had to either delay or forfeit a match because he was wrestling on another mat. While it may not be a big deal to the offending wrestler, it leaves his opponent high and dry. His opponent shouldn't have to wait for or miss out on a match because someone else wants to wrestle in two brackets.
That being said, I'm all for being able to "wrestle up" in a non-qualifying tournament.