No, the bike isn't exactly BMX, nor is the fork. It is pretty good for a 6 year old, however.

As for U-brakes, I'm sure they are fine for someone with a strong hand. But for a small child they just require too much force on the lever. I checked. The Magura rim brakes will work perfectly if I can mount them. Hydraulics are wonderful. I do realize they are not really necessary for typical BMX use by teens or adults.