I worry what other people think as well - however, it really does help if the people you are going to have children of their own. They seem to understand better.
My first baba loved her sling, so I could bundle her up next to my chest and enjoy the night with friends - when she wakes, she'll sit up and when tired, she would lie down in the sling and sleep. Number two is less forgiving on my social life and does not like outing or the sling. So we usually go to friends with children.
We usually take a camper cot and monitor with - I keep to babies routine as much as possible. It helps keep them calm. I feed and bath normal time and then take him to a room away from the people when tired to settle, feed and put baby to sleep. I have my monitor with me, so it puts me at ease once baby is asleep and I get to enjoy the eve while I know my boy is save and sleeping.
This usually keeps you busy for the first part of the evening, however, it does leave you free to relax and enjoy grown-up conversation later on.
Do phone before hand and find out if she would mind you using a spare room and if you can bath your little one there.