We started our daughter on a Santana Arriva when she was about 5 using a kiddy crank, then she progressed to a crank shorteners and it was great. We used normal peddals with cages because I was worried that her feet could slip off of the pedals at speed and we never had an issue. We use to go on club rides of 30+ miles and she was great. We also ran a rack with panniers that she would use to take along her stuffed animals, in particular we use to travel with the entire Lion King family. On hot days we would take squirt guns and she would be the tail gunner cooling down club members as they rode up to us. We would also take several snacks that I would keep in my jersey pockets so she could get to them while we were riding. We also did a Santana tour of the San Juan Islands when she was about 10 and again she loved it and we never had an issue with the long days, but we did have frequent stops.
About a year ago my wife and started riding the Arriva again have just upgraded to a Beyond. We haven't really talked about if we are going to sell the Arriva but if you are interested and can get it up to the bay area from either SoCal or Paso we can talk. I have long ago sold the kiddy crank and jsut recently gave my crank shorteners to someone the forum so no longer have the kid parts.