I want to add a couple of things:
1. You can add park-hopping later. If you are undecided, you should probably buy the base ticket, then add park hopping if you decide you need it.
2. I like park hopping - there are definitely days when you want to be in a certain park in the evening, but not in the morning. But,it is cheaper to buy more park days then it is to buy hopping. I am staying for 7 days, and rather than spend 4 or 5 full days in the parks, we decided to spend 7 partial days. The 7-day base ticket is the same price as the 4-day base ticket.
3. Consider hopping to non-Disney parks. My kids really want to go to SeaWorld. For under $50 you can buy a 7-day pass to Sea World. We plan to hop to and from SeaWorld, instead of another Disney park. You can consider doing the same thing with Universal.