I don't know, but our cabana experience at the DLH has always been that the cabana host isn't there often enough to even notice. We saw our maybe twice. You have a server, too ... we saw her more often but like any server, she's working for tips so I doubt would say anything since more people = more food and drink = more tips. The cabana host will be there first thing to show you around then maybe once or twice after that. Maybe don't have 7 first thing. Otherwise I'm not sure they would even notice.
Here's how little attention the cabana host pays: One time I went up to our room to get something and the phone happened to ring. It was our cabana host, wanting to know if we were going to make it that day. We'd already been there over an hour and my family was IN THE CABANA at the time he called!
The main issue, and probably the main reason they say 6, is that it would not be comfortable to have 7 inside the cabana, at least not 7 adults. There are two smallish sofas that will fit 2 adults comfortably or 3 if you're really friendly! There are also two chaise lounges, but those are just outside the cabana. If your husband is trying to work, having 7 people, including 2 kids, could be a challenge unless most of the people are elsewhere alot of the time.