My personal opinion is that you will spend more money if you book 100% the way you are planning. They count on you wasting some of the perks you pay for.
Also, we always book about a year in advance for our hotel, flight, character dinners,etc.
I deal specifically with the airlines I deal with day to day which are American and Southwest. You can get good deals on their websites if you book enough in advance. For June... you are in a prime travel season but it should not be that bad, depending on your originating airport.
I worked directly with WDW for book my hotel and character dinners, etc. We always stayed at the Polynesian which is on the monorail line and one of my all time favorite hotels. I LOVE that place. It is pricey but worth it (at least to us). The Grand Floridian is another favorite and very nice.
We never did a meal plan. I don't like limitations when I am on vacation and being told where or what my eating options are. We are not huge diners anyway, plus we usually stayed in the Concierge tower of the Polynesian which has a small breakfast, snack, lunch, snack, happy hour, dinner and dessert provided daily with unlimited drinks, fruits and light snacks 24 hrs.
You should be able to have your vacation for $3500. We have spent as low as $2500 (free airline tickets) to over $7000 which was all Concierge, private safari, unlimited tickets, etc.
Good luck, I am sure you will have fun!