Lua and I did this 5k without the boys. It is very tiring to push a nearly 50 lb kid in a trailer working like a jog stroller.
It was cold and windy but we stuck it out and finished the race. I don't know how Josh puts up with pushing the stroller. It was hugely unpleasant. I'm looking forward to Lua learning to ride a bike so we don't need to use the stroller for races, even if it means a season of pushing a kid on a bike.