I am traveling with a part of 10. We're looking into staying at Caribbean Beach, but my travel companions are thinking they might want to save a little money and stay off-site. We are going to be there August 24th and 25th - so a Sat and Sun - likely visiting MK and Epcot with no park hoppers. We want to ride the new rides - we haven't been since 2020 so Tron and Guardians are at the top of our list. Our friends have never been. I, of course, want to stay at a Disney hotel - its what we always do. They are finding places that are cheaper and keep asking about the benefits. How much will I regret not staying on property as far as being able to maximize the 2 days we have in the parks?
It might help if you list some of the options they are considering. I wouldn't worry about getting/not getting G+ or ILL's that time of year. At any time of year, it is possible to miss out on the 7am virtual queues. If so, you can try to the 1pm drops, and have a good chance of getting them, or just pay for the ILL's.
You can save quite a bit of money staying offsite. There are many VERY NICE offsite options that are better than the WDW hotels in many ways. There are also some dumpy offsite options too, and/or options that might be a trade-off of some kind.
A plus of staying onsite with a bigger group is that everyone can come and go to the parks as they please by bus. That is possible offsite, but a bit harder. It is especially helpful if everyone travels together in the morning.
Going to WDW with a large group that has different interests is like herding cats. In my experience, it is best to give them what they think they want. If you force them to visit WDW your way, they'll just hold that against you. Even though you know the wisdom of rope drop, and staying late, and everything else.
On the other hand, if they are happy to do something your way- like rope drop or eating somewhere fun, they will probably thank you for your expertise. There are just times when giving them their way = a smoother trip.
You can lay some ground rules, and try to explain the trade-off costs. With a group that big, it will be hard to do all the rides you normally do, but it can also be great fun filling a whole boat, and eating together. Two important rules are to have everyone (mostly) take bathroom and snack breaks together, or the day can get very chaotic.
There is also the consideration of how you will travel between WDW and the hotel. Free offsite shuttle buses are often a pain, because they don't come/go very often. Time is $ at WDW. If offsite, having a car or uber is better. Onsite, everyone can use the free buses/boats/monorail. In August, afternoon breaks are very helpful, so that might be one reason to stay onsite. Afternoon downpours are somewhat common.
Also, that time of year, you will do well to make sure everyone has plenty of water! Somehow, have plenty of water on hand at all times.