discourage jumping by turning away (facing the way the dog is)... (of course this is hard to teach your 2 year old to do!)...
keep turning away until the dog gives up.. don't yell, or shriek or knee him (although usually I have seen 2-3 flips - on carpet or soft grass PLEASE - which takes fortitude and is not without risk cure he behavior, please don't start with that. or continue it).
Also you can have a toy or food of high value to the dog, and show him - with your hand sliding down your leg (As your back is to him) - that you have it in a fist. and use it to lure him into a sit. then turn, face him and be sure he holds the sit - at first he will only if you keep the food over his head... then give him a piece.
Step back, still facing him... bring your hands together at your waist - with food/treat in one, saying "name come" - if he launches, turn and repeat. If he comes but does not sit, lure him in to a sit gently and be happy voiced with praise as you give him the biscuit.