HI L.,
My daughter is under a year old, so we're a bit out of the playdate loop, but I wanted to respond to your post. Moving to any new area can be tough for kids...especially at the ages your kids are. It can be very cliquey. Then to add that they look "different" from the other kids at an age where they are all seeking their identity and looking to be as "similar" as possible, is extra tough. I just wanted to encourage you to hang in there...and not give up. Maybe if you can meet some parents and invite a family over for dinner or dessert or an activity and encourage your kids to approach another child when they are alone and not in a group of kids,it might help. Once the other kids are in their "groups" it can be hard for anyone to break in. Actually, as a new mom, I'm finding a similar situation myself with the other "veteran" moms in the neighborhood!
I am sorry to hear that there is still such ignorance out there, especially regarding race. I know there is, though, and experienced it myself. I've worked at a medical office in PG now for 3 years as the only "white girl" as they called me, in the practice. I welcomed that experience and learned a lot. It did take a while for patients and even some staff to be willing to get to know me, and some people were even blatantly hostile about my being there,and these are grown and educated adults! It didn't take long before I fit right in and loved it there! Now, there have even been tears that I'm leaving to be a full-time-mom! I like to think that this experience has broken through some ignorance on both ends!
Take the time to explain to your children that people tend to be anxious and even afraid about things they don't know and that can include someone who looks different than them. If, by chance, they are learning this negative and ignorant behavior from their parents, let's hope the kids will lead and teach the parents a thing or 2!! Encourage your kids to continue being friendly and I am sure things will turn around.