Regradless of the size of your group, you will never save money paying for concierge service.
Concierge is not a meal plan, other than breakfast there is nothing that's a meal. There is nothing but some Goldfish crackers and candies at lunch time, a cheese and cracker tray and ahot appetizer before dinner, and some deserts after.
Additionally you'd need to take time out from the parks to be at the resort during this time.
I'm not sure how large your group is, but keep in mind that deluxe resorts charge $25 per person for each adult after the first two per room.
Anne