On a regular basis, the older and younger children play and work together. For years now we have a buddy system where an older child works with a younger child. Often this involves art work, board games, and also constructions with Lego. The older children teach the younger children and they have lots of fun playing together.
This works really well for everyone involved and it helps to create an atmosphere of support and trust amongst the children.
Our experience with the buddies is overwhelmingly positive. The older and the younger children love it similarly. It is great fun for both. And as a side effect there is a lot of informal learning going on between them. This, by the way, is also true for the older ones who are often in the role of the expert who is asked for advice.