We just returned from a trip in November with a Grand Gathering (GG) with 13 people. It was actually a nightmare from the beginning with Disney.
We were told we could book everything through the special GG number but the CM's who answered the phones didn't show interest in doing much of anything other than selling us GG packages. This wasn't just one bad CM but we called at least 15 times and hung up feeling that way at least half the time. Other people in our party were disappointed with the service they provided as well.
If all your people are staying in the same resort and dining at all the same restaurants, it should be okay but they really fouled up a lot of things with our itineraries. I don't think we had a single meal planned with all 13 people due to different arrival/departure dates or other plans. When they mailed us our itineraries, not a single one was even close, let alone accurate. We had to follow up with several calls to straighten everything out.
We should have just booked our ADR's through the normal number and left it out of GG's hands. Even after having them confirm everything over the phone, we still found reservations under one person's name and another's phone number, wrong party sizes, etc. A real mess!
When we did check in to Coronado, we didn't get the building we requested nearly a year earlier. Three of us wanted to be in three different buildings for various reasons. My family wanted the building closest to the food court so we could be close to get food for DD and have use of the microwave. They put everyone in the furthest building so we would all be next to each other. I asked if they could change this when we checked in but they couldn't because they were full.
We only booked one official GG package and it was the Safari Celebration Dinner at AK. Everyone in our party had mixed feelings about it. We all agreed that it was fun but not worth the money. The description said you get a private, personalized safari and that you would be stopping a lot so they could give you more information than the regular safari.
Well, they didn't stop at all. We were free to ask questions to our guide but they just kept driving at normal speed, leaving us feeling really rushed.
After this we all went to Tusker House for the dinner portion of the package. The food was okay though I can't fault GG for this. They did have musicians playing in there which was extremely loud so it made having a conversation with our party really difficult. I don't know if the restaurant is normally like this or not as it was our first time there.
Overall, the safari and dinner were fun but not worth the money. We would have been better off riding together and then going to AKL's Boma for dinner.
I strongly encourage you to book everything yourself except for the GG packages instead of letting them do it for you. Again, this may not be an issue of everyone is doing the same things.
-steve
Edited to add: I noticed you have 8 people in your party. As I recall, a lot of the packages required a minimum of eight people so if anyone in your party won't be doing the activity, you may not be able to book it. The CM's at GG can tell you for sure.