Looking for tips or advice on how to manage a 3some sex date.

Background:

I fly a lot for work, I have a FWB/part time GF (lets call her, Winnie, sex with intimacy, less commitment) in one of the cities I visit quite frequently. So, in one of the dates about 9 month ago (we had sex for more than 2 yrs at this time), she texted me, asking to bring her BFF (she did took photo of her BFF for me, and ask if I wanted to fuck her before (lets call her Nina), I always shrug it off as it was a joke or test) to come over and have fun, this was about 2 hrs before our arranged time. At that time, I was mixed with surprise, confuse, and alert. So I think with my bigger head and politely rejected, saying I might not be able to manage the complex relationship, of course, my smaller head say "fuck yeah, both of them".

Some time after, was casual chatting, Winnie brough up the idea of inviting Nina again, so this time I had a serious talk with her, and well, small head took over and say, we will try to arrange it.

Present:

For the next few months, I suggested we get to know each other online first, we have a common chat group. Then that progressed into having individual chat with each other and group chat, which private chat is more private and intimate (nude photos and etc), which both are aware of the private chat, and I would share sharable knowledge with each other, censoring some privacy or intimate content.

Over this period of time, some intimacy also developed with Nina, where Winnie is well aware of.

Now:

So, after all the mis-timing and hurdles to get 3 ppl together, its finally going to happen next week. During these few months, I also scoured the internet for tips on how to plan for the event (most articles are on how to manage/maintain the relationship) without much help, then I thought about asking it here.

Few things to have in mind:

1. Had sex with Winnie for about 3 yrs.
2. Havent met Nina in real life, but she insisted she wants to meet me with Winnie together (I suggested to have a 1 to 1 date first for buffer).
3. Both women never had 3somes before, Winnie is more open while Nina is more shy.
4. My 3some experience are limited to paid providers, and invited to couples, never manage it myself.
5. Both women express high enthusiasm and expect a good fuck.
6. At this stage, they have no interest to be on each other. Its like Winnie is sharing me with Nina, thats my understanding, and assumption.

Any tips or suggestion? My current plan is to wing it, maybe start right away with Winnie after they got into the room. And not have the awkward moment between closing the door and taking cloths off.

Thanks.