Let me start by saying I generally agree that the 6D is the optimum choice for your needs.
But if you do go crop, here is another thought. Considering the needs, many of what the 70D has over the 60D probably don't matter for your needs.
The main benefits are more AF points, which probably don't matter much for static objects, AF in video, which you don't do, WiFi, which you expressed no opinion about (I don't think) and AF micro-adjust which I'm not sure if it may or may not benefit. I would think this type of photography is mostly manual focused anyways where I would guess the micro adjust wouldn't matter? Not sure - I don't have the feature.
I brought up the 60D because it is half the cost of the 70D right now and would leave a good $500 towards a lens.
I guess the question is, have you been disappointed with the image quality from the Rebel? If so, then you probably won't be happy with any of the Canon crops because from what I have seen, they haven't improved much since the T2i. I'm not saying they are bad - I was happy with mine as long as the ISO stays down - but they haven't made any great strides in improvements.
I don't recall if you stated anywhere about what your old camera lacked that you hoped for in the new camera, but that's where you should make comparisons.
I'm in a similar boat with different needs/desires. I just sold my T3i and have been looking at the 6D, 60D and 70D. However, my main subjects are my kids (my daughter plays soccer as well) so I have some concerns about the focusing of the 6D for my needs. But also, I really want to use it for video and I haven't found my skill levels up to manually focusing in video, so I usually just don't. Also, I have the 15-85 and 10-20 Sigma crop lenses and I figure to replace them with say the 24-105 and 17-40, I'll probably spend another $1200+ over the 70D and the glass I already have (and this is a hobby for me) just to get back to the lenses I have now (of course they would be much better lenses).
For these reasons I am leaning toward the 70D, but what I really want (and probably everybody else) is the 70D with a full frame sensor. Another words, I prefer everything about the 70D over the 6D except the FF part and I fear the 6D2 will have dual pixel tech and then I'll be wanting that one. So part of me says get the 60D (better than the T3i I had and I didn't have AF video anyways) and wait for that one. In the mean time keep building glass (and lighting).
Anyways, maybe what you should do, if you can, is rent a 6D and see if it is what you really want. I thought about renting one, but I already know the outcome.