I also recommend a lower gear and brakes. I pull my daughter all the time in her Burley without a problem. But that bike has both brakes and crazy low gearing. Depending on the load something in the 60s should be good. My gear is in the 50s but I like to keep a decent cadence when I'm riding with my wife and I occasionally off road with or without the trailer. My daughter loves the "bumpies".
Craig