Earlier in the game, most of the activity is either with him watching (in the room or from elsewhere) or, on occasion, optionally participating (that is, the player has a choice to make him watch or participate), but there are a few encounters that happen without the husband's knowledge (though he does hear about them later), even right from the beginning of their adventures.
Later in the game, the majority of Anne's activity is either seen by the player but only related to the husband later, or seen by us while she's relating it to her husband. There are exceptions — times when the husband is present — but they become rarer. Some of this is dependent on whether or not Anne is defined as cheating, but that affects fewer scenes than you might think.
The direct answer to your question, though, is that there's very little sharing in which the husband is also a participant. One scene with Mike, one scene with Dre (but the player can choose to keep the husband on the sidelines, which Anne prefers), and again at a swingers' party (where it's one of three options). There's also a cuckqueaning scene in which the husband can participate semi-anonymously, but it's only one of four possible options, two of which aren't cuckqueaning at all. Finally, there's a scene with another woman whose husband is interested in pursuing a similar lifestyle, and if I remember correctly there can be a threesome (Anne, her husband, the woman) during that storyline.
That said, the vast majority of Anne's activity doesn't involve her husband, except as an enthusiastic cheerleader either before, during, or after the fact. The same is true for the husband's activity; with a small handful of exceptions, she doesn't know about it despite occasionally complaining about that fact, and he never tells her about any of it. There are, depending on how you play the game, a growing number of encounters that I think we can assume happen, but that no one — including the player — ever sees or hears about (e.g. the likelihood that, every time Anne gets on Martin's plane, they're having sex).
I'm leaving out a number of factors that are affected by the player's choices, but it's most definitely not a swinging or active participation story. It's a willing or mostly willing cuckold story, that's the husband's fetish, and that's what the majority of Anne's scenes are.
