I had to book ours (for the end of May) for one person at a time. It would not let me copy over to the rest of the group. So all five of us each have a different time, but they are all overlapping somewhat. (Actually, the two farthest apart don't intersect, 10 to 11 and 11 to 12, but I am hoping they will let her go in with us at 11:20, when I believe all others do intersect.) What a mess!
Incidentally, it did let me book my 3 year old by herself. Everyone else in the family has a time overlapping with hers, but she has her own time.
So our party of 5 is taking up 5 slots, instead of the one we actually need. Sure, we'll take longer than one individual (unless it is a very chatty individual!), but we certainly don't need that many slots.
Thanks for the booking one at a time tip. It was the only way I was able to find anything.