I don't have any first hand experience packing people into the 6 GC, but I have spent some time in the back of one myself. I'm 6' 4" and 165 pounds, and I fit pretty comfortably behind the driver's seat set to my normal driving position - pretty impressive as most cars and SUVs will not allow for this. The 4 + 1 is, in my opinion, like my 6er coupe is a 2 + 2: the "+ __" number is BMW's attempt at making you think that you're getting a little more practicality in a car that prioritizes style and performance over practicality (more so in with the coupe than the GC). I think the fact that the 6 coupe + 2 in the back is a joke. I very rarely put anyone back there because the act of maneuvering to get in there puts a lot of Nappa and alcantara in harms way with shoes, fingers, and hair touching many, many surfaces. I imagine that getting someone to straddle that center console is probably about as graceful an act. The sizes of your kids will likely make a pretty big difference in putting the puzzle together in a way that they are least uncomfortable (I think this is probably better terminology than "most comfortable"). While my first thought is "the smallest goes in the middle," that would likely involve little feet kicking around trying to get over that beautiful center console, so maybe someone with longer legs who has a little more distance between the Nappa and the Nikes should sit in the middle - I don't think headroom is likely a problem given their current ages.
I'm trying to think this through as realistically as possible, but I'd imagine that any trip requiring 5 to fit in a GC is likely to involve some arguing over who gets which seat. I think it really comes down to the choice between:
1. This car is for me, so I want the more elegant, sporty, exclusive option that will perform more like a sports car than a big German limo. If we have to go on a family trip with all 5 members, then we'll take the wife's X5. I'll give up driving the GC on family trips to have it for all of the times when I'm by myself of have a maximum of three passengers.
2. I'm at a point in my life where I want a big luxurious sedan that is powerful and fun to drive, albeit not as fun as a GC, that gives me comfort, luxury, and power on a daily basis yet affords my family the same level of comfort any time we go somewhere as a group of 5. This will be the go-to family car as it has the most passenger space and comfort of any car short of a Phantom.
For me, it would come down to the amount of time you need to haul around 5 people. If it is a few times a year for a 30 minute trips, then it would be the 6 GC. If I want to have my luxury saloon for work but be able to use it for going out with the family (instead of the X5) every weekend, then it would be the 750Li.
The new 7er is a thing of beauty that has great presence and looks very impressive, more so than the outgoing model even though this is only an LCI. The 6 GC, however, is going to catch all of the admiring looks. I guess, putting it bluntly, people see a 750Li and think, "Damn, that person has made it and is obviously very successful," while people will see the GC and think, "Damn, that car is gorgeous. I would kill to have one of those."
That's just my interpretation and thoughts on the matter. I don't think you can go wrong either way. I think it just comes down to how much you want to use this car for hauling around the family vs. how much you want a car that can pretend to be an M3/M5 (I know this is an exaggeration, but you know what I mean) but can also carry the family.
On a final note, have you considered the M5? A little more space than the 6 GC but performance that will kill the other two (especially the 750Li). I assume you have considered this option, so I'll shut up and stop babbling :rofl:
Edit - right after I hit the "post" button I read your closing comment "If it's not workable, I'll have to go with the 7." This sounds to me like you really want the GC and would find the 7er to be a compromise. I think, after rereading that, I'd say go with the 6 GC and use the X5 for all of your family trips. The X5 is capable, so I'd say have a little fun and go for the GC :thumbup: