It really is a catch 22 here.
If you run big brackets then people go else where for smaller brackets and mat time. If you split it all up then the really good kids start to complain about seeing the same 2 kids each week and the if theres a scratch etc etc etc
Sometimes it is also an issue of mat space and the number of matches per mat etc etc etc
I say take the mat time but also find the tournaments that you know will run the big brackets.
This late in the year big bracket is the only way to go in my opinion.
When you run a tournament its hard to please everyone.
Just attend the tournament that tend to run the kind of brackets your wanting.