Cat has some good suggestions and don't forget to put up flyers, call the shelter, and so on. Facebook has ended up bringing a lot of animals home, so that's not a bad idea either.
Cats are survivors and they do sometimes wander off and then reappear days or even months later. Hopefully you'll be reunited with your babies. I'm sure you won't let them out again.... most of us have probably had indoor/outdoor cats at some point but have learned the hard way about stuff like this. So don't feel like the Lone Ranger.