We are both Chinese and we live in Zurich. We will hold a wedding next summer in Zurich. Lots of friends will fly from China for the wedding. Now we are about to send out the save the date. The questions now is how to deal with plus one/two/three.
On one side, it's quite common to plan a vacation with parents or even grandparents! (we have a lot of friends who are in 30s, single, only child) and we already know some of our friends are planning this now. It is also common to have a vacation with partner and kids (we also have a lot of friends who are in 35~40s, recently-married, have one or two kids). All these would mean +2 or even +3.
On other side, of course we can say no. At most "+1" or not allowing "+1" would also be an option. This would mean our friends leave their parents/family alone in the city and most likely they don't speak english.
I guess this problem is kind of unique. But maybe somebody has had similar considerations?
PS. After writing this post, it's a bit clearer in my mind that allowing at most "+1" might be ok. For those who need +2 and/or +3, those +2/+3 people can hangout by themselves.