I see a problem here. How, without discussing sexuality that goes over childrens heads, do you portray, in a Cartoon where features are naturally exaggerated, Homosexuality without resorting to stereotypes, in a way that small children with no real understanding of sexuality can understand? This alone would be nearly impossible for even the most skilled animator, never mind the fact that overly sensitive homophobes are right there to make a huge fuss. If you manage to do it great, but I'm not sure how reasonable it is to expect that. A kids cartoon probably doesn't stumble randomly into the issue of homosexuality, and having a plot point dependent on homosexuality runs the risk of the kid just seeing Homosexuality as different. A better solution would be one that is about as old as kids cartoons: Teach tolerance, acceptance, and respect for people who are different, and let the kid realize for themselves that this applies to gay people when it comes up.
And actually, Rainbow Dash is the only character I can think of in a kids cartoon that handles this, and handles it well. I kinda identify her as Bi, but in a manner I suspect will never come up in the show itself, and is actually kinda cheating through the rainbow imagery (Also, its not shoehorned imagery since its based on a pre-existing character). The beauty of her character is that no one will ever be able to say that she is gay or bi, but a kid might actually recognize certain traits that are associated with homosexuality, but not exclusively so. It's so subtle, I couldn't tell you what they are, exactly. And the fact that it is a complete non-issue is perfect.