One of the clubs we go to is BBW friendly. It is also a 35 YO age limit. This allows people to be relaxed without having to worry about what people think about size, age, etc...we've all been in the Lifestyle for 10+ years so there's a lot of communication and if you hit a wall with a question, there's always someone around who's been there, done that, who can assist with a new point of view.
That said, you've already communicated online, w/pictures so there are no false pretenses here. They are agreeable to you and the reasoning is that they like the combination of what they've read and seen. It's a package that you've put together that is presented as a fun couple who is comfortable with themselves and want to share that fun with others, and not just sexually. The groundwork you've laid will lead to a friendship that can last for years.
OK, I'll shut up now...