New and don't know where to start

My son has shown a liking for things that spin, and anything that makes things spin. Also trains and tractors. I love lego. I want to combine our interests and hopefully provide him a gateway into robotics later. So I am looking for suggestions on where we can start with lego technic that focuses on functions. I'd really like to get into pneumatics as well which seems to also fall into lego technic. Anyone know where I should like, begin, for this? Thanks in advance! submitted by ...