Great idea as long as the quality is high, as has already been discussed.
For school, one problem with doing things on bikes is getting them there. Separate bike transport can considerably increase the cost of a short whole class event. Smaller groups in an after school club would be more successful but would this just target those kids who would go with their parents at the weekend ?
Have you thought of contacting one of the national "forest schools" which are springing up to provide specialist education for those who need something different ? eg link
Forest Education Initiative - providing teachers with learning resources on trees, forests and forestry products