I think I remember you saying from another post that you are quite new to poly? I'm quite new too (16 months) and I think it's very normal to be feeling apprehensive about all of these new situations you find yourself in.
One thing I've found it that the fear of these events is worse than the actual event.
In fact, meeting the person can help *so* much with any jealousy feelings. It also gives you a chance to show your partner how wonderful you are by being charming and welcoming to this new person
Is this their first time actually hooking up? Or have they hooked up before you meeting them? If it's their first time, I think that does add a little stress for you... but it's great that you've got work to distract you.
The best advice I can give you... is keep your chin up, be brave, put your most charming hat on and get in there. I promise that you might actually have fun. Let us know how you get on!