jacksbike

I have used an Alley Cat brand 1 speed pedal trailer for both my daughter and son. I have used a front low-rider alloy fork rack with small panniers in order to carry stuff. This has worked out well for the fact that there is no way that I can use a rear rack on my bike (previously a 10 year old Trek 7500 hybrid and now a new Trek hybrid ) because of the trailer attachment to the seat post. The front lowrider racks have a low center of gravity and as long as you do not overstuff the small to medium panniers you will be OK.
When I used a Burely d'Lite covered trailer there was plenty of room to carry all of our junk. Now with the pedal trailer I am more limited. My wife usually rides with us and has an alloy rear rack on her Ladies hybrid in which she has mounted a rectangular trunk rack.
Other ideas: A small square handlebar bag to hang on the childs trailer handlebar: a handlebar bag to hang on your adult bike.
Good luck !