bit vague / your interests?
Three months is not enough time to hit all 48 states & actually SEE or DO anything.
How much of that three months is in Hawaii? At what point/date in the trip are you flying out and from what city/state - to Hawaii? That will give us a better idea how to direct your route.
Are you interested in city life / national parks / scenic routes / hiking, etc? Give us some ideas to pinpoint you in a direction. Do you have budget$ limit on types of things to do/places to see?
Sounds like fun! Be sure you are compatible with those going with you or it will quickly become a nightmare. Even though you are friends in school, travelling together 24-7 can become a strain.