I know that planning your first Disney vacation can be overwhelming, but we're here to help! My first piece of advice would be to get your hands on a copy of Passporter. They were an invaluable resource to me when planning my first trip and I know they will help you as well.
Park hopper passes-I think they are great and very handy if you don't mind spending the extra money for them. However, they are also not a necessity and one of the first ways that I recommend people trim their itinerary if they are traveling on a budget. We nearly always travel with an Annual Pass so we have the option to park hop, but we very rarely actually do it. If we do, it's generally toward the end of our vacation when we want to hit our favorite attractions 'just one more time'.
The meal plan takes some calculating to determine if it's right for your family. It is very right for ours, and we always purchase the dining plan. My best advice on this would be to visit
www.allearsnet.com and search the word 'menus'. This very comprehensive site lists detailed menus for every restaurant on property and has very recent prices listed as well. If you decide where you'd like to dine you can get an idea from there what each meal would cost you. As a general rule, if you plan to eat a lot of table-service and character meals, then the plan is likely to be a good fit. If you're happy grabbing a sandwich on the run, then you could probably save money by forgoing it.
I ran out of room before I could get to the must-do's, but PLEASE feel free to ask us another question! It helps if we know if your children are boys or girls too, so we can get very specific. :)
I hope this information helps you, and you dive into the planning with gusto. After the initial intimidation I found planning our first Disney trip to be a lot of FUN, and I'm sure you will too. Have a great trip!