We do the DDXDP on all our trips.
3 meals - either TS or QS and 2 snacks per person per day. Also you get the refillable mug, they will pick that up in the Food Court.
The dinning & snack credits start as soon as they check in and end at mid-night on departure day.
Depending on arrival time and departure time.
Here are a few suggestions to get the most out of there DDXDP meals.
Book Character Breakfast most of these are buffet so plenty to eat, snack mid day, and a later romantic dinner, we love to get the last possible seating especially in Epcot, we have been lucky to be walking out without hardly any other guest around, This makes for some great pictures, there is normally a cast member who has taken some pic's for us.
One of the days I would do an early lunch so that they have a morning or two to sleep in

Sci Fi or LTT or Chefs are really nice spots for lunch.
I would do at least two signature meals, Flying Fish 1st then Cali Grill 2nd are great. Yachtsman's and Narcossee (sp?) would be my next choice's.
Depending on departure time, you might be able to squeeze a really nice breakfast in for the last day. Kona or Grand Floridian Café. If they are leaving later Lunch at DTD at Raglan road would be great a then they can stop at Goofy's Candy's and use up any remaining snack credits. If they are in a time crunch, they can always get QS to go.. for at the airport. Also if they have a super early departure time, tell them to use the remaining snack credits up the night before at the bakeries, and candy shop's.
My DD got married this year and the had a Mickeymoon too. We and some family members gave them Disney Gift cards at the reception, which they really appreciated and said that it gave them extra spending money which is always nice.
Also don't forget about photo-pass this makes a really nice wedding or shower gift.
Congrat's to the couple