I think because you are not sexually attracted to them you are in a much more delicate situation. The situation isn't whether you can get your friends to play with you. And your question about whether they are swingers isn't important either, as I see it.
Here's what I see as a possible outcome. They finally let you know they want to have sex with you, and then you have to say no. They won't like knowing you've been so flirty and sexual with them - knowing you are swingers - only to be turned down by you.
Or, they may never want sex with you, but enjoy the teasing, nudity and kissing. How much sexual activity and for how long will you want to continue this since you don't find them attractive sexually? Will seeing her boobs get boring after awhile? Somewhere along the road I'd be concerned that your friend's desire for play with you grows to oral or fingering and you won't want to go there because you are not sexually attracted to them. How would they handle your rejection? How will you feel rejecting them? These are the things I'd be most concerned about, not about whether to label them swingers.
LM