Hi, Keith!
Let's start with the Dining Plan: With a 4 year old, I would probably stick to the Base Disney Dining Plan which includes 1 Table Service, 1 Quick Service, 1 Snack (each per day) plus your refillable resort mug. The Deluxe Plan will give you 3 full meals per day. Unless you are planning on Signature Dining, or several Dinner Shows (which will require 2 Table Credits per meal,) then the Base plan will be plenty of food for you and your family. Click
HERE to read about the different meal plan options.
Now onto the Park Hopper: My family does a lot of park hopping. If you plan to take a mid-day break each day (highly recommended!) then having the hopper is a nice option since you can then switch parks for the second half of your day. However, if you simply plan to do a 5-6 hour stretch in a park then call it a day, then you will not need to add the Park Hopper option. It is about $54 to add the Park Hopper option to your ticket (regardless of how many days are on your ticket) so weigh the cost against what your realistic plans are for visiting the parks.
And finally, Minnie and the Princesses: Character dining is a great way to meet many of your favorite Disney Pals! Try Chef Mickey's at the Contemporary and Akershus Royal Banquet Hall in Epcot. Character Meet and Greets are also in each park, so check your Times Guide when you start your day in a park for the Disney Friends' schedules.
Wishing you and your family a very magical Walt Disney World vacation!