I sort of agree with the comments above. FRC is pretty hard, and I'm not sure mini-FRC is much easier. Making things smaller doesn't always make them any simpler. At any rate, it can certainly get very pricey. Especially for control systems, if you're using a full-size IFI RC there. The good thing about Vex is that you can get most of the stuff you need in one kit for $300, which is steep... until you look at a full size RC.
I will at this point mention the
BEST robotics competition. For those that haven't heard of it, it runs on a fundamentally different model than FIRST. There are literally no entry fees to teams. A team puts down a deposit to cover kit items that must be returned like motors and controllers. All fundraising is done by the equivalents of regionals. Teams can only attend one, and must win to advance to the next level. Same 6 weeks time frame. The important difference is that teams are strictly limited to the materials in the kit of parts, and the robots are 2' x 2' x 2' and 24 lbs. And not programmable (yet). So it's a smaller program than FIRST in some ways, but capable of reaching schools that are very unlikely to have a FIRST team. As for the programming bit.... BEST is working on DSP based programmable controllers... and I'm working on BEST to look at shamelessly co-opting the VEX controllers.
The key point of the above is that there is no entry fee to a BEST team, though. FRC has an entry of $6000, FVC is $500 or so plus two Vex kits. Your mini-FRC competition would be around $500 or more for a new team. BEST is free. Or free, pending a $200 deposit. So, if there's a BEST hub in your area, you might consider pointing pointential FIRST teams at it before you terrify them with a $6000 entry fee.
EDIT: Oh yeah. BEST is in the fall. No worries about it interfering with build season.