If I already booked a room for myself, boyfriend, and child and it's a large room for 4. Am I able to add another person to that room as well? Would it cost any additional money for that person to have a waterpark pass? If so how much?

No you don't need to call them as you would get 4 passes as wrist band as per room size or family size even though you booked for 3 persons in reservation. Reservation counter at entrance is friendly and huge. It went well for us and we were left with 1 spare pass.

Yes you can add another person. The cost used to be $25 hope that helps!

You can add another person it might cost some additional Money but that doesn't matter you will still have a lot of fun with another person with you.

Call and tell them you want to add another person to your room. If it's a room for 4 its priced for 4 so you shouldn't pay anymore.