You don't have to run in the wave you sign up for either. At least that is how they've been around here. It's just to try and have some order but you request a start time and can actually run any time. So they can do different waves and take care of the baby themselves.
But I love the advice to talk up how you can't wait to not have to worry about children! And if they ask I would not be tactful. I would burst out laughing and say "you're kidding right?".
Good luck at the Warrior Dash!! They had that out by us at the beginning of July. It was a lot of fun. I went to take photos of a friend who was running it. H and I may do it next year.