I haven't found a good strategy yet for dealing with dogs while towing the kids in a trailer. Before the trailer it usually wasn't too big a deal just to outrun them. Now acceleration and terminal speed are way down (or the dogs have gotten much faster).
Last year my wife was riding on her bike solo while I towed the trailer. She hit a dog that cut between us to get at the trailer and went over the bars for a rather severe crash. Bad road rash and some bruises but it could have been worse.
Dog spray is illegal in this state and even it it weren't the kids are in the windstream and would be easily hit with the overspray.
I've tried the water bottle squirt and the yelling. Doesn't work for most of the dogs around here. Note also that the dogs are generally focusing on the trailer. I'm more worried about cars swerving to avoid the dog and hitting us than anything.