Janet2k pretty much summed it up. If they want to enjoy the benefits of the concierge lounge they should spend the money to stay in a concierge room. Several reasons for this, the first being space. The lounges can get quite crowded during peak times, and the extra bodies take up space that should be used by paying concierge guests.
Also, they won't be able to get to the lounge without a key for taht floor, building, or section of the building depending on the resort you choose.
There are plenty of spaces that you can all meet other than the concirege lounge, including the lobbies. Depending on which resort you choose there are plenty of seating areas. Some of the resorts also have some wonderful nooks and crannies. AKL and GF have excellent seating areas in the lobby.
If you really want a place wher eyou can all met, why not share a 2BR villa at one of the DVC properties?
If you are trying to justify the cost of concierge exclusively in food savings, you probably won't be able to. They do not serve full meals. Other than breakfast you will need to eat elsewhere. The only place I found enough to be able to pass on lunch was the GF, and that's only because I had a large breakfast in a full service restaurant and it had gotten beastly hot so we weren't really hungry anyhow. The dinnertime offerings are appetizers. One of the rudest things I've ever seen was a family who literally cleaned out the appetizers leaving none for anyone else, and then bragged about how they didn't have to spend money on dinner. That same rude family came back later and cleaned out the desserts.
Anne