Hi Anne and welcome back to the Disney Parks Moms Panel! We love when guests return with new questions and I always enjoy answering questions for fellow North Carolinians.
How lucky for your husband to have a convention that has the ability to purchase special convention tickets! In the case of a ticket having a bonus visit option, the bonus is just that, a bonus. If you plan to spend three days in the Theme Parks and one day at a Water Park, you would purchase the 3-day ticket with a bonus visit. Be sure to check the expiration date of the tickets to be sure they won't expire before you plan to use them!
I'll take just a minute to recommend my favorite Water Park at the Walt Disney World Resort,
Disney's Typhoon Lagoon. I could spend all day floating in Castaway Creek!
Please let us know if we can help you with any other questions!
Wishing you a magical vacation,
Amy H.