Hi there Maggie!
You are planning one year ahead! That is so great because it gives you some flexibility! When I graduated from High School, (way back then) I wanted to go Walt Disney World!
Your family is going to have a wonderful time! I did a little bit of research for you... Walt Disney World is busier during Spring Break than in early June. There is a great FAQ section on the Disney Web site that lists the
busy times of the year. If I'm not mistaken, Resort room rates are lower in early June as well.
Now, if you really want to impress your daughter, you can take her during
Disney Grad Nights! It's a night just for high school seniors to let loose in the Magic Kingdom, after hours! They have Live DJs, Dance Parties, and Special Fireworks! The link is for this year's Grad Nights because next years dates have not been set. I hope this information helps in your planning a Magical Time at the Walt Disney World Resort! If you have more questions please let us know we are always here to help!