I also booked June 15th and 16th just after the kids are out of school. Rumor has it, the ride will be testing the first two weeks of April. That's Spring break for some. But I wouldn't book a trip based on rumors. Thus, the June trip when school is out.
IMHO, I think the Mummy will open in April so it can be the major ride opening. Problem is, USF is not letting anyone know. So guess what? People from up north are not booking trips to come down. People need a month to book a trip.
Example. I just saw an ad for a west coast event at SFMM. It's being held March 7th. I booked it today, a month in advance. The plane rides are less, there are seats on the plane, and I can plan. For some reason, the marketing department thinks everyone can plan a trip and execute it in a week. Like I'm going to see a commercial, and boom, drive up the next day. It doesn't work like that. Trips are planned months in advance.
USF should be telling people an estimated opening date of the Mummy ride now, and running ads up north, before CP opens in May.