You mention that they walk a lot with you. My dck, too. The little ones (15 to 16 mos) walk for about 20 to 30 min for field trips about 4 days per week. The older ones (2yo) about 45 to 60 min both ways. That is a good exercise too. All of the other kids move around a lot when outdoors in top of the walking, except this girl (at least I think she is having a good exercise by walking 20 to 30 min almost very day). She is less active than the others, but still much better than when she started. I guess it has to do with how in shape they are or the way of how they are getting in shape. If your 4 yo dcg is carried everywhere in the stroller and she is allowed to watch too much TV at home it seems she is not getting too exercise often outside daycare hours. IMO If parents aren't encouraging physical activity and healthy eating habits we as daycare providers can only offer opportunities to practice their gross motor skills and healthy meals during their time with us, but we cannot force them to be active and eat.