As for the "hard training" worries....
Is anyone else remotely disturbed about this new trend: http://news.yahoo.com/s/ap/20080327/...U5bwlu0tdH2ocA
I don't really care for MMA or the UFC, because of the general "brawler" mentality they invoke. I'm also concerned that this hard mat training would *not* be very good for a growing child.
It's quite obvious you have no first hand experience with any sort of that training.
We do MMA training at my BJJ academy. The BJJ component, as I noted before, is very much derived from Judo (and my academy, as well as the Judo schools around here, either has offered or offers Children's classes). Children's Judo and BJJ is perfectly acceptable, isn't it?
The takedown portion of the class is taught by a wrestling coach. That's wrestling as in elementary/ middle / high school wrestling, which is percieved as very, very common and perfectly acceptable, depending on your school district.
The striking training (kick boxing) is not too dissimiliar to any striking training that involves protected contact (like forms of Karate, TKD, or Muay Thai) that involve younger folks all the time.
It's very hard for me to see why a hybrid curriculum, under proper supervision and with a good teacher, is so bad at all if the separate components are all acceptable, just because it's called "Mixed Marital Arts."