Unfortunately there is another issue. Lift operations are often cut back after the 3rd weekend in April. Mt. Bachelor's practice in recent years has been to cut back lift operations (no Northwest, Outback and limited backside access) and hours (close at 1:30PM) after the 3rd weekend in April. There has been no flexibility in that decision, though in fairness I have put a call in to ask if the late Easter might make a difference. The tentative response is that they wait and see how business is going in the spring, but my question is being passed up to the marketing director.
Mammoth has closed Canyon and Eagle Lodges after the 3rd weekend in April in recent years. However, Mammoth's operations are based upon conditions and demand more than the calendar and are still likely to close at 4PM in your time frame. I have called Mammoth and they intend to maintain full operation of lifts and Canyon/Eagle lodges to April 24 because of the late Easter.
Without an expectation of full operating hours and lifts from Mt. Bachelor, I would choose Mammoth for that week despite the La Nina.