Hello and welcome to the boards. My first advice o you is to do a search on any questions you may have in case you don't get a lot of responses to your posts. There are hundreds of posts in various forums that can answer a lot of your questions. Plus it is also good becaus everyone has an opinion and it is nice to get a variety of different opinions. Here is my two cents:
1) May is a nice time to go. Like another poster mentioned, it is warm but not stifeling. The only thing I will say is you are going to encounter a lot of school field trips and softball tournaments and cheerleaders and soccer teams etc. There are going to be a lot of young adolescents.
2) The dinig plan is worth it but there are a few questions you need to ask yourself first. Are you interested in attending a sit down meal every day? And if you are, will EACH of you eat an appetizer, a meal AND a desert? Same for counter service, can you all eat a meal and a desert? If your answer is no then the dining plan may not be for you. My husband and I did the dining plan in September 2005 and loved it. At the time it was free so it was a REALLY good deal for us, LOL. But we have gone back since then and have not gotten the dining plan and I don't think I would PAY for it. It is wonderful but we simply do not eat that much food in a day especially at WDW. It gives you one counter service, one snack and one table service per NIGHT of stay. That is a lot of food. What I recommend doing is going to Allearsnet.com and checking out the menus. Add up the prices and see if it is cheaper to do the meal plan or to just pay out of pocket. I did this for me and my husband and figured out that money wise it was just better to shell out the money if we wanted to do a sit down. On the other hand of that you get to eat at some amazing places that you may not normally eat at because they are so expensive. Example, Le Cellier in Canada in Epcot, we ate there when we had the dining plan, we looked at the prices and we were stunned. It was amazing food however I would not have paid that for a steak dinner. Plus you can use your table services on Character breakfasts which is great if you are interested in doing so.
3) YES, YES, YES. It is absolutely worth staying on property. You have so many perks and conveniences from staying on property. You can use the transportation to get to and from the parks and you can take advantage of Extra Magic hour. (in case you are not familiar with extra magic hours that is when you can stay at the park a few hours later or go an hour early depending on which park is doing it for that day, only available to people staying on WDW property). Plus you have that Disney feel...
I would recommend Polynesian for Deluxe accomodations, Caribbean Beach for moderate and normally I would say All Star Sports for Value because that is so cheap and my absolute favorite however that is where all the adolescents on the sports teams stay whe they come. So for a value I would say either All Star Movies or Music. (I have never stayed at POP Century).
4) Never stayed at Port Orleans but have heard some very good things. Again, do a search and you will find alot of opinions on these various topics.
5) The absolute BEST character meal (in my opinion) is Chef Mickey's at the Contemporary Resort. They have the classic characters, Mickey Minnie, Goofy etc, the atmosphere is fun, they sing and dance and are constantly at your table, and the food is amazing and very kid friendly. And if your kids like putting M & M in their cereal they will be in heaven!! My second favorite is 1900 Park Fare at the Grand Floridiean, excellent breakfast, made to order omelletes, characters like Mary Poppins, Alice in Wonderland, Tigger and Winnie the Pooh. The Grand Floridian is gorgeous too! And the third runner up is Donalds Restaurantasaurus (spelling?) over at the animal Kingdom. Again, classic characters, great food. Allearsnet.com will tell you each character breakfast and what they serve.
6) No idea on this one. We usually stay at Value's nowadays and when we do bring the kids we are at the parks all day long.
Have a great time!!!! :wave: