Personally I would not worry about the pedaling and get your little ones onto a balance bike (or run bike). The hardest thing to learn on a bike is balance - once you have mastered that then pedaling is the easy bit. Little kids often don't have the leg strength to pedal, especially on hills.

DP put a video together on this FB page called "Why a runbike?" so check out DD1 on her journey to riding a 2-wheeler with no training wheels when she was still 3 - he has put in heaps of information on the sorts of bikes and reviews etc there too. Welcome to Facebook