Most (all?) resorts have a coffee maker in the room, but if this isn't desirable for whatever reason and he's going to purchase coffee at the hotel each morning, buy your husband a refillable mug for $17.99. Individual cups of coffee are $2.89 a pop. As long as he buys 1 cup of coffee a day (and let's face it, 1 cup isn't enough), it pays for itself.
Sharing CS meals is the way to go. WDW food is expensive, but the portions are huge across the board. I have a big appetite-- especially for "vacation food"--but I can easily share WDW meals. Last month, traveling with my 5yo and another adult, we'd typically order like this at a CS: one combo meal with fries, another meal entree only (no fries), kids meal with 2 sides (typically the choices are applesauce/grapes/yogurt/cookie/fries). We'd all easily share the one pile of fries, and the kids meal sides would get saved for when my son got hungry and crabby later. And we still all had trouble cleaning our plates.
I'm all about bottled water at home but the free CS water tastes just fine to me, so keep that in mind as another cost-saving measure. Happy planning!