Definitely plan the type of shower the honored parents would want. If everyone invited didn't all live in the same neighborhood, would you even consider how other folks covered childcare?--I doubt it. But since you are a close neighborhood group, and you are inviting couples and not just moms (leaving dads to babysit), you can do one of two things:
1)Make it an official family event where kids are clearly invited. Then you, as the organizers, would be in charge of hiring a couple of local teens/babysitters to keep the kids occupied during the shower.
2)Make the shower clearly for adults only and spread the word that people who need sitters may want to consider getting a group sitter(s) at their house during the shower. This puts the responsibility for childcare on the people who need it and not on you as party planner. If your child is old enough now and you need a sitter too, I think it's perfectly fine for you to ask if any other neighbor would like to volunteer their home for the sitters. If no one steps up, get your own sitter, and let the other people find someone on their own or stay home.
Personally I think it's enough for you to be throwing a party for your friends. It's great that you're trying to be proactive and find a solution for your other friends--and maybe you'll set the precedent for future neighborhood showers--but other people's sitter problems shouldn't even be a concern of yours.
I've always taken my kids along anywhere they're welcome, and I know how nice and easy it can be to just go places as a family, but I also understand how great it is to hang out with only adults, and your parents-to-be should really get that if that's what they want.