Welcome to our forum.
I've heard many stories over the years of swingers making the transition to polyamory, and the stories always have a good deal of fear and insecurity over adding emotions (and commitment!) to the sexual mix. All I can tell you is when it works, it works well, and it's really worth it. Most of the time it does work, as illustrated by your own story. How wonderful for the four of you to be able to open up to each other in every way!
Have a look around on our threads and boards, and learn as much about polyamory as you can. Communication is probably the most important topic to explore, and always will be as it's a lifelong learning experience. Try a search (or a tag search) for "communication," and check out our Golden Nuggets board
as well; it covers a lot of the basics you need to know in a polyamorous life. Above all, post and let us know any time you have a thought, question, or concern you want or need to share.
Don't know how relevant this is, but I should mention that I know a few polyamorists who are also continuing to be swingers on the side. So poly and swinging aren't always mutually exclusive, they can have some overlap. Your four-person family (I think quad would be the right word) can decide whether you prefer to be exclusive to each other, or whether you want to allow each other to "play on the side."
In any case, I hope Polyamory.com provides you with friendships and insights, and enhances your poly experience. Glad to have you aboard!