I don't have experience with the Apple river but we have done it with my niece and nephew when they were younger probably about 5ish on the Muskegon river. The nice thing about that river is, there are a couple of places you can start the trip but it is still an all day thing. Of course the weekend floats are a lot of people having a floating beer party. Might be another option for you to look into however.

Semper Fi