What do you think you need to upgrade on your current body? What is it not doing for you right now? Are you being hindered by its ISO performance during sports shooting? Is the rest of what's going on solved with a flash instead? Or are you just itching to buy something new? To actually get an AF upgrade, the 7D and 70D would be the two crops to look at, but even then, do you need them? Are you having problems tracking kids sports with AI servo?
If you really want to step up your tracking, a refurb/used 7D would be smart. The 70D would be a good choice too, but do you really need a $1k camera that does basically what your camera does now, but with a little better AF system and a stop better ISO performance and that's basically it? Is that worth $1000 to you?
My vote is to save your money. Maybe get a tripod + gimbal and focus on technique, and focus on learning to short sports better (maybe you're already topped out for your current equipment, don't know, haven't seen your work). I don't see a camera upgrade being worth it for you for what you're shooting. The only thing I can think of, is that actually, faster glass would be more beneficial.
If I were dedicated to shooting kids sports, right now, I'd probably get a 7D and a 400 F5.6L and a 2nd 7D with a 70-200 F4L IS.