For action/sports shots with the kids, the 70D is a better choice. It's AF system, frame rate, and the "extra reach" of a crop camera are better for that purpose.
The 70D has a 19 point AF system, with all 19 the better/faster "dual axis" type. 5D/5DII both have 9-point AF system, while 6D has an 11-point, and all three only have a single "dual axis" type point at the center. All the rest of their AF points are slower "single axis" type. So, 70D will be far better acquiring and tracking moving targets. (Note: 5D/5DII have 6 "hidden" Focus Assist points that can be used optionally, but aren't shown in the viewfinder. Enabling these essentially makes the spot metering circle in the center act like one bit AF point. Two of the "Assist" points are dual axis type, but the "Assist" points only work in AI Servo. And, for low light shooting, the 6D's center point is able to focus about 2 stops lower light than any of the points in any of the other cameras.)
For macro, a FF camera can be good because they tolerate smaller apertures better (because you end up enlarging their images less), but you won't really see much advantage unless you are making very large prints from your images. 70D's articulated LCD screen can be an advantage for some macro photography... none of the FF cameras have that.
FF Fanboyz and Fangirlz are everywhere these days! But today's crop sensor cameras come awfully close in image quality and croppers have a number of advantages. Crop cameras can use all EF and EF-S lenses, while FF cameras are limited to EF only. In general, lenses for FF are bigger, heavier and more expensive. Compare an EF-S 10-22mm for a crop camera with an EF 16-35/2.8 II for FF. Or, compare an EF 300/4 IS for a crop camera, with an EF 500/4 IS II for FF.
The ideal thing to do is use both formates.... each for it's own strengths.
If you shoot a lot in low light and/or make really big prints from your images, FF might be right for you.
But if you shoot a lot of action/sports and/or the largest you ever print is 13x19", even 16x24" or so, you'll likely be better off keeping the crop sensor camera.
As to those "disappointed" by the IQ of a crop camera... stop pixel peeping. Be realistic about the final use of the image. Even if you make huge prints, you won't be looking at it at 100% magnification after you're done editing it.
You tell me... Which of the folllowing images was shot with a FF camera and which with a cropper? (The same lens and filter were used for both images.)


Maybe a higher magnification detail from each image would help?
Or maybe not.