Would it be manageable to take 4 AP classes in my senior year and?
Typically these classes tend to give problem sets that have fewer, but harder problems. Make sure you stay caught up on any reading that's assigned and you'll be fine. If, however, you decide to save everything the day before a test or a quiz, you will regret taking those classes. Oh and make sure you understand what a derivative and an integral is. You'll need it for E&M.