I don't think you/ her should do anything you're not 100% comfortable with. When my wife decided to start fucking another man, it was locked in that i'd always be there... she knew as a cuck it was important to me, so she also wanted to see me happy. But over time, that gent became a friend, and sometimes it was next to impossible to set up our regular Saturday night, dinner/ drinks/ sex. Work, *******, her period, etc. just prevented it.
But after a while, daytime meets at his city apartment would be possible for her and him as they both worked in the city, plus as a woman working in the corporate world, she was always dressed impeccably, which was important for her when we all caught up.
Anyway, we/ I decided, as a cuck if I really wanted her giving up her pussy for him as often as possible, this was going to be the most convenient way. I wasn't cut out, it just became convenient for all involved. I still get text messages, pics or the used condom if they used one later as a memento and that really helps me still feeling involved.
So, if your not 100% about her going there, I wouldn't do it until you've worked out the dynamic and the reasons they don't want you there, may just be an ease factor thing, or he can't perform with you there.