If it's that important to you, here's what I suggest.
Let it happen a couple of times before you mention it to a ref. I really dislike it when a coach comes to me pregame and asks me to watch for something.
Approach the official during a timeout and ask him how long the timeouts are supposed to be. If you are correct, politely ask that he enforce it. Something like, "I'm doing my best to finish my timeouts on time, and he's getting extra time to coach his kids because of it." If he says no, take the extra time with your kids.
Alternatively, you could approach the game management (tournament director) about it and ask him to have the officials enforce it. You may want to feel him out to see if he thinks it's important enough to worry about.
You also might want to verify the lenghts of your timeouts.
I can't guarantee either of these will work, but I can guarantee a lot of other approaches won't work.
