I was thinking of a couple of things....
First, is there a way to talk to you DH and figure out what it is about family vacations, esp. disney, that stresses him out? Is it the people, the running, the cost, what's going on back at work that he's missing, not being able to get away from the kids EVER? Not having any personal space or privacy? Perhaps knowing that a bit better might help you figure out good ways to combat it. My DH stresses about the cost and never having any time alone. So I always talk up the savings that I'm getting, make him a part of the decision making about what/how we're going to spend the money, and plan some time where he can be alone.
Golf? Does he golf? Or play tennis?
Have him leave you one day mid-day, maybe. Tell him that you've just gotten him a new book (or newspaper, or magazine) and that he gets time to go to the hotel, sit by the pool, and read. Or that he has the hotel room to himself for a few hours to nap, channel surf, or whatever.
Is it possible to build in an extra day off when you get home. Sometimes the stress of getting off a flight, or after a long drive, going back to work the next day can be tough.
Get him in the game. Get him a t-shirt or sweatshirt of his favorite characters. Get silly Goofy ears or mouse ears and take tons of pics. My mom believed that anyone and everyone who ever went with us to DL (I grew up nearby) was required to wear some sort of Disney apparel. If they didn't have anything Disney on, she abuducted that person(s) and immediately went to the Emporium and they quickly had something. (People learned to pick out their own beforehand, as you never knew what mom would get you there!

) But I tell you, it worked! People were smiling and joking about it all day.
On the night that you plan to have alone time, either have the entire family leave a bit early and go back to the hotel to play in the pool, watch a movie, order pizza, or maybe even send them with a gift card to Build a Bear, if you're concerned about impinging on their "Disney Time", OR, your friend might be able to stay in the parks with them for the last hour or so. I don't know if this is the case the night(s) you will be there, but DCA closes earlier, typically, than DL. Maybe have that evening be at DCA and then you can say, "well, everything is closing down, time to go." I'd recommend, if you have a car, going down to the beach area and have a bite to eat and walk along the beach. If you ate earlier with the kids, then maybe going to one of the bars that over look the beach (I know some in the Redondo Beach area, but there are beaches a lot closer) and get an appetizer and a drink and then wander around the beach. Gives you a Disney break, is romantic, and I've never found anything quite as soothing as a walk on the beach after dark.
Good luck! It's so sweet of you to want to help your DH!