When they come to me for help, I divert them to their sibling for assistance as much as possible. Much of the time this gets them cooperating, and is usually good for a laugh as well. They each have their strengths, and get a lot of satisfaction in being the one to be in charge.
We've gone for a few rides around our flattest block, which is about 4 miles. Towing 7O lbs behind my bike is surprisingly hard given my lack of fitness, especially up hills. The kids really like the whole process, particularly their cup holders in the pod. I make sure to select a route with cows, sheep and horses to ogle, and we sing the whole way. This is, actually, exactly my vision of parenting toddlers when I fantasized about it pre-child. Nice to have ONE fantasy come true.