Maybe you could invite a neighbor over for a brief shabbos afternoon play date/shabbos party?
It would give your kids a chance to get to know each other. If your kids are older, you could extend an invitation for either a meal or dessert. You could tell them “I see you here a lot, but I don’t have a chance to get to know you. Maybe you’d like to come over for dessert or a play date this shabbos?”
I think the time to think about making friends is not when you need them. By then you’re too desperate to think clearly.