First, welcome. I'm going to cut through the usual on this one and get to the important bits.
The way to look at this is like anything else in life, though there is one key detail, you CAN change your weight, but beyond that it doesn't change. If you have red hair, are very short, are very tall, talk funny, have one eye higher than the other, bad teeth, good teeth, B.O., perfume, small tits, big tits, *insert race* here, etc etc SOMEONE will reject you for that reason. Likewise someone would play with you, perhaps for that reason. Its a cliche but there is someone for everyone out there, even in swinging.
Now lets go a bit further. Clubs often get a bit stereotyped. Some are known for people being more fat, others for more skinny people, some seem to attract an interracial crowd, etc. In my area, you would have no problem with your weight with one club we know of, and would be completely rejected by another. Its going to be up to you to explore where you fit in best. As a rule, you will be limited to couples in your same weight range, and before someone tells me otherwise, its not universal, tastes always vary.
As long as you go in with the attitude that not everyone will want to play with you (and this applies to ALL couples regardless of looks) you will find people willing. The question is of course, are you attracted to them as well.
My wife and my weight have yo-yoed quite a bit since we started swinging. Interesting to us, was a few years ago after the birth of a child we got back into swinging and at the time we had both let ourselves 'go'. New baby, lack of motivation, playing computer games (for me) made us heavier than we had ever been. We STARTED to get back into shape and thought we were 'pretty good' to put an add up. Well fast forward another year of mild work outs and better diet. I happened to be going through an old computer folder and found those original pictures. I showed them to my wife and we both had the same conclusion, we would not have have swung with OURSELVES the way we looked the year before. Perceptions can change as you are happier with your own looks.
Now the one good thing you can do that others can't for their potential looks issues is lose weight. Its worth it on so many levels beyond just swinging. You can prevent a bevy of long term health issues which you could be on a collision course for as well as feel better with how you look so you don't need to wonder if you are too fat. You are both, give or take 20 lbs, almost 100 lbs over weight, this WILL get you with time. Its hard but it only gets harder with time. Swinging can be a GREAT motivation for working out and dieting, so run with it and help yourself beyond making it easier to find play partners.