"The other alternative would be to run two boats with just your group on them and one boat with the six other divers at the resort on it in the morning, and then move those of them who are doing 3 tank packages to the boats with your group for the afternoon"
At this point, does the resort even know how many of the "others" are doing the afternoon dive? Doesn't sound like it to me... Do we really want to shun six of our divers who aren't doing all three dives? Besides, even though we are a group, it's not like we all know each other and dive together all the time - by the end of the week, the "other" divers will be a part of us anyway...why not get to know each other early?
We'll make the best of it and have fun regardless of the split...