^If I ever have a divorce, I want it to be like that. It sounds like you two were both really mature about it, latinluva. That's awesome.
But back to this topic of affairs outside of marriage, I mean really, does it have to be an affair? That word seems to imply cheating. It really depends on what you define as marriage. Really it's more of a legal term, in terms of your status to the federal government, banks, assets can become joined, etc. But the vast majority of people look at marriage as a vow of monogamy or true love, etc. That's why you have the wedding in the chapel and the day before you went down to the town hall or courthouse or whatever and got your license.
So could you be married and not be legally 'married'? Yes, as in just a promise of true love, monogamy, some couples just never get married, but they never really stray either. Can you be legally married and agree that you can have an open relationship or are just doing it on a whim or can have orgies and whatever you want? Of course.
However, it's the married bisexual who has taken this vow of marriage/monogamy or led to convince his wife that he has and then goes out and cheats with someone of the opposite sex under this guise of 'I'm a bisexual, I need both kinds of sex' that is someone who lives a narcissistic selfish life, hurting others at the drop of the whim.
But if your spouse is all for it, go for it guys! Just let them have some fun too.