Easter weekend will be busy, and more expensive than non-holiday times. If your kids get out of school in May, go then. Many, many school systems won't be out of school until sometime in June, so May will have smaller crowds than later in the summer- and not be so beastly hot! The prices in May will be better, too, as will availability.
Check out mousesavers.com for tickets from
Undercover Tourist. If you sign up for the mousesavers newsletter, you can get a link to
UT which will give you slightly cheaper prices than UT's regular prices. We have used UT many times for Disney tickets and they are very reliable. Another way to get cheaper tickets is to go through Disney's YES program, but I am not sure how that works or if it's available during your time- but the ticket prices are amazing!
I would rethink using the dining plan. I know many people love the "no worries" aspect of it, but it's never been a good deal, financially, for my family. I can usually feed 3 of us for about $250 less than what the dining plan would cost. As we fly Southwest (which lets you take 2 suitcases, per person, without baggage fees) I pack breakfast and snack foods and take them with us. Our breakfasts usually consist of mini-bagels and cream cheese/pb/jam, fruit (either fresh or fruit cups), yogurt, cereal. I freeze the yogurt and pack them in an insulated lunch box, with an ice pack, and they ship just fine. (I put the cups in a ziplock bag, just to be safe). I'll buy milk for the cereal at our resort, although DD21 will eat hers with UHT-packaged almond milk). Sometimes we share meals, but only if it'll be enough food to satisfy us- and there are always snacks! Go to allears.net and check out menus/prices and estimate what your family would actually spend on food to determine if the dining plan is a good deal or not.