Hi there, Melinda!
Most of the "cool rides" - as in, those the big kids love to visit! - offer a single rider option (some, like the
Rock 'n' Roller Coaster Starring Aerosmith actually have a separate physical line for the single riders).
You can take both of your children through the queue at any ride, and when you arrive at the front of the line, let the Cast Member at the entrance know that your older boy will be riding alone. At that point, you might even ask for him to be seated with another younger rider in a multi-passenger vehicle, or whatever suits your comfort level.
Once you have seen him seated, you can immediately proceed toward the conclusion of the ride, either by the exit or, if the Cast Member is amenable, to the area where each Guest leaves the ride vehicle. This way, he is never far away, and the chances of him wandering into a shop without you are minimized.
Please be aware that most of the rides feature security cameras monitored by Cast Members whose job it is to ensure every rider's safety on board the ride.
While this might not be as thrilling for your two-year-old as riding it's a small world, you can make the queues fun by bringing along small toys, cars, and, of course, snacks!
Have a wonderful time!
See you later, celebrator,
-Deborah B.