How high is your fence? If it's 6' or more, and secure as far as holes or weak boards, you're probably ok. Personally, I'm not a fan or the wireless/electric fence as they involve shock collars (we won't even get into that whole discussion here). Do keep collars and tags on your dogs at all times. I think *most* people are good, and if they find dogs running loose, will make an attempt to help them. If the collar and tag are easily visible, it makes it easy to read, call, and hopefully reunite dog and owner quickly. I have both cell and landline #s on mine, along with their address (dogs get out of gates, I've returned countless dogs to homes with owners absent but gates left open). I also have mine chipped - in the microchip info, the vet info is included, and clearly they know my dogs. They also wear their vet tag - they could be ID'd that way. If you think your dogs will be "of the wandering kind" and likely to get out, you may want to look into one of the GPS tracker collars - I think for dogs who are houdinis, they're a good idea. Personally, mine wear their collars w/tags including their home info, a tag from the rescue where they came from w/ their ID # (who also has my info), and their county tag (also would come back to me). I don't think there's any way to guarantee that if someone picked them up, they'd have to return them to you, but if they were taken to a vet, their microchip would show different info from their owners so it may raise a flag. As I said before tho, I think *most* people are good, and will do what they can to help an animal in need.
I think we have to be careful, we have to have them ID'd the best we can, make sure our fences and yards are secure (that includes holes under fences), keep up with training (that includes know to never run out a gate unless given permission), and make our bond and relationship with our dogs the best we can. I don't think there's anything that's 100% guaranteed in life, especially when you're dealing with living breathing beings (and I'm speaking of both dogs and humans here). But I think if you do the very best you can, you'll be ok.