MOB drills are ALWAYS a good idea. Panic is the first reaction of the unknowing so you have to teach them not to panic. Always keep a set of eyes on the last known location of the man overboard. This helps in maneuvering the boat for the pick up.
I've taught many people to sail. And just when they think they are getting comfortable, I'll throw a jacket over the side, make the call, and sit back to watch how they perform (individually and as a team). No one expects a man overboard but they sure better plan for it. It is an immedediate action item. This means you have to respond from memory instead of spending time to think about it.
With advanced crews, I'll intentionally fall in and act unconscious or not knowing how to swim. With any crew, getting back to the man overboard is only half the battle, you still have to get him onboard and treat for any injuries, inhaled water, hypothermia, etc.
It might be different on a lake in Iowa.

In that case, take your time, pop a cold one and let them swim to the boat or you'll see them on the next pass. YMMV
3 yrs of age is not too young to be teaching him how to swim. At least in calm waters.
It's somewhat distressing to realize 99.99999 of the gen'l population don't know First Aid or CPR. It's probably the same % of boaters and MOB. I've saved the lives of 2 people because I was there and knew what to do. I'm just a guy, I'm not in the medical profession or a first responder. But we all have this responsibility, especially so when going out on the water.
This is important.