We are/were in the same boat with no family living close, and finding child care is always a hassle.
Two tips that worked for us.
The best babysitters are teenage girls just barely young enough to not be seriously into dating yet. Poll your circle of friends and acquaintances and see what you can find. Look for someone mature for their age (which is why girls are a better choice at this age than boys IMHO) and responsible, and then just have them babysit overnight. (btw, your kids will probably love that, pretty soon they will be asking when you are going away overnight again ) Especially if her parents live close by, she will probably be comfortable with that, so will her parents, and so will you since she has some trusted adults to call upon that are just a few minutes away if need be. Problem with that is, they don't last long. Give them another year and they have their own active social life to maintain, so you have to start all over to try to find another good one.
Especially when your kids get a little older, then sleepovers are your friend. Host plenty of sleepovers, and in turn your kids will get invited back, and there you go. Swingers aren't the only parents that need overnight babysitting, so pretty soon you will probably have someone to call upon should you need a kid-free night as long as you return the favor when they need the same.
It's a hassle and takes some advance planning, and when you get both couples in the same situation, then finding a date that works for everyone may take months, but just be patient and it's doable. Good luck