All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If wine is not sold openly in that restaurant and there are no open violations of other prohibitions, then there is no harm to respond to that invitation. However, if there is any clear violation of the Sharee’ah, then one should not be there unless he is able to change it.
For more benefit on being present at a place where alcohol is served or drunk, please refer to Fataawa 351544, 90464, 86497, 85631, and 82521.
Allah knows best.