According to the Wiki I have basically three options:

1. Go to the presidential suite with Benny
2. Go to the presidential suite without Benny and be ambushed, after which he will be captured and taken to the Fort by Legion
3. Kill Benny

I went with option 2, but I didn't go to the presidential suite straight away, opting to look around some more first. As soon as I exited the tops however, I was approached by the Legion stating that Benny had fled (rather than taken) to the fort. Another quest entry is added for me to inspect Benny's room, where I can speak to Yes Man, and after which the Ring-a-Ding-Ding quest is completed for 1000xp, even though I haven't visited the presidential suite at all. If I now visit the presidential suite after completion of the quest, I am still ambushed and Benny is still talking to me over the intercom, yet he supposedly allready left and all the people in the Casino are talking about Swank being the new guy in charge.

What the hell is going on, what am I supposed to do and how does this influence the game?

Oke, well thanks, guess I'll just kill off the ambush team then. Was just wondering whether it might be an alternate ending where Benny is not captured by the Legion, but jusy happily sleepsover at Caesar's crib or something.

Regarding the ambush team, I can just get past them with a speech check, but it seems awefully unrewarding to do so. At least you get to loot four corpses if you get ambushed.