Wow, you make it sound so easy! Haha! Ya, what you are looking for us possible and we here tend to call it poly. I am in a vee situation like what you are looking for with Mono on here and PN for example. I also have a relationship with derby on here and have other relationships too. The point of it all is you can create what you want/need. Its suggested, as its been tried and seen to be true that it works better, that you should have honesty, open respectful communication, empathy, a pace acceptable to all in it and in full knowledge of the effects of NRE.
Good luck and happy reading here. Bring your wife, the more the merrier.
On another note, its great that the site you went to suggested here! Thank them for us would you? Everyone has their way and I am glad someone saw that and passed you on to a possible better fit.