Hi and Welcome to the DIS!! You will learn wonderful things here!
Just wanted to throw out one more suggestion for you.
Renting DVC points. We did that the last time we went and I have sent multiple friends and family this way over the past two years. It really is easy and the most cost efficient way to go to Disney and stay in the deluxe resort for moderate prices.
If you are going in May and can plan your stay to go a Sunday through a Friday you will be able to stay at Beach Club Villas, Boardwalk Villas, Old Key West, Saratoga Springs or Wilderness Lodge Villas for about (or less) than a Moderate stay. These are known as Disney's Home away from Home resorts and they are wonderful resorts. Since you are a family of five with a Baby you will be able to rent just a studio which will give you a great deal more room than a POP room or slightly more room with a Kitchenette (microwave, sink, refridge and toaster & coffe maker)than a Moderate size room. The layout of a Studio is a Queen Bed and pull out double bed.
The best thing about renting DVC is that you get to go to those great location resort (especially Beach Club and Boardwalk for the Epcot area) By the way I think Swan/Dolphin have separate buses, but BWI and Beach Club share buses. Someone else will probably be able to answer. But both of those resorts have boats to MGM and EPcot. You would have to take a bus to MK and AK though.
Anyways. There are some cons to renting and that is you have to do the transaction with a DVC owner and not through Disney. We have rented with four different people and everyone of them has been great. There is a rent/trade board Under DVC Timeshare section of the boards. That is where you would start looking for a renter. Another Con is that you can't do a "package" if you rent DVC. You would have to buy your own tickets separately and you would have to do your own dining. SO if you had your heart set on getting Dining with your trip that would be out. We think the location of having easy access to Epcot at Night and MGM far outweights paying Disney for Dining, especially since we usually pack PBJ for our kids!
Just a quick look at a point calculator for May shows a Sun-Friday stay of 5 nights would equate to 65 points which most renters rent for $10.00 a night equates to 650.00 for your accomodations. Now that would be for the Beach Club, Boardwalk and Wilderness Lodge for a Studio for any Sun-Friday stay in May. It would be only 600.00 for Saratoga Springs and Old KEy West (okw has two queen beds instead of a sofa, this is the biggest room offering for a studio, good deal for $600.00 for five night accomodations.)
Anyways I would check out the DVC forumn if you think you want to know more. Also Check out this link at Mousesavers.com to get a better idea of what I am talking about
http://www.mousesavers.com/dvc.html#rentpoints
Hope this helps, and of course you can PM me with any questions.
I always feel the need to tell families that can fit into a studio and who would benefit from a quick return to the rooms about these options especially for the BCV, BWV and WLV! You could do the plan you mentioned except you can hop over to Epcot at night since it is just a quick 5 minute walk from BCV and maybe a 10minute walk for the BWV. Or the WL will give you a boat to MK! Also the pools and kitchenette are wonderful with small kids because we ate breakfast in the room (ceral, oatmeal, bagels-- loved having that toaster) Also, going back for nap is easy and great pools to hang out at! Also at BWV and BCV you can watch the fireworks from Epcot out at the Lake and that would be almost as exciting as hopping over there!
Hope I haven't confused you!
Cmbar