My MIL had a portrait of all her GC done for her 60th.
Two of them, ds (8) and his first cousin (14) have AS. To be honest it was a nightmare from start to finish.
The photographer just couldn't get them looking natural, kept trying to get them to look into her eyes (rather than saying look at the camera) which as you can imagine, was a non-starter. She also kept trying to pose ds, which was also a disaster as he has limbs like spaghetti that just flop and won't stay put for more than two consecutive seconds and his core strength is extremely low, so her idea to arrange the GC sitting, one behind the other, in height order, within the 'V' of each others legs on the floor was an unmitigated disaster, as he was at the back, desperately trying to hold himself up with his arm, whilst trying to look but not look at her face. 
Needless to say the resultant photographs were - er - um - terrible (and that's being polite). We were given one as a Christmas present and strangely, we haven't been able to find a frame we like for it yet. 
The main problem with them is that ds doesn't look happy and relaxed (which is what people usually expect from a family portrait) instead he looks stressed and uncomfortable - not exactly an image you want permanently framed on your living room wall. 
Such a shame as well, as he really is quite a handsome chap and usually really photogenic, but then we tend to take pictures of him when he is happy and relaxed, rather than trying to pose him.
We were told when we agreed to do it, that the session was going to be relaxed sort of reportage style with the photographer taking pictures of all the GCs just playing and being themselves, such a shame they didn't do that, as it would have suited him much better and allowed the real him to shine through.
I definitely think it would have helped a lot if the photographer had had some SN awareness, as when we tried to interject and say - ds can't do that or he will struggle with sitting in that position, she just waved us off and said she'd photographed hundreds of children and she knew what she was doing. 