based on what you say, I'd go d5100
i'm a happy d7k owner, together w the already legendary 85mm f1.4 G, as well as the humble but very nice 35mm f1.8, and the 18-200 f3.5-5.6
the 18-200mm is not without flaws but it's a good deal better than the 18-105mm on optical quality and mechanical quality and AF speed - ie would serve you quite well for sports
once you have that, the 35mm provides better low light but due to its also rather slow AF, becomes bit redundant
and then if your budget allows, add the 85mm f1.4
hopefully, buying a d5100 vs a d7000, will help
if I did it all over again, I'd buy just this, the 18-200 and the 85mm f1.4. I'd skip the 35mm f1.8 which is nice but not that useful once you own the 18-200mm (or course if you don't have the 18-200mm then it's different but you can't shoot much sports at all)