OCJD, my DS is 7 (nearly 8 now) and sounds similar to yours, right down to the "crushes" that some of his girl classmates have had on him (though I think first/second grade crushes are a little different). It's possible that he will begin hanging out with these girls less the older he gets, but I haven't seen any sign that this will happen (and much of the class has already started to segregate by sex).
I'm not particularly worried, as he seems capable of finding friends almost everywhere he goes. It's more that, given a diverse group of kids from which to choose, he goes for the girls (often older girls).
P.S. I've been pre-approved to be an in-law by a couple of the parents, too.
