We have had this situation come up a couple of times, and had it work out a couple of ways. Once DH and I ran into some friends during food and wine, and We had ADR's at Chef's and they added them to our table ( from 2 to 4) we had to wait a extra 15 minutes but it was not a problem. Another time we were crossing paths with some friends that we don't get to see often... really rarely ( party of 5) it was their last night, and our check in night (party of 3), nothing was available for 8, But I did get a ADR for the 3 of us. We were at Crystal Palace, so after explaining to the hostess, she said she did not think so but would try to work something out. So we ended up at 2 four tops along the window they were back to back, so the adults sat at one table and the kids at the other and we had the same server so it worked out well with the bill. All the kids were in middle and high school so perfectly fine to sit together. Another time some friends took a long weekend trip for their anniversary and at the last minute ask us if we wanted to join them for dinner one night, I got so lucky and was able to get a ADR at Le Cellier for us.. We were 8:10 and they had 7:45. We went about 7:00 to find out, They said no can do... plus she said they were running about 15 to 20 minutes behind, so at first we decided just to dine separately then, we walked over to England and the guys got a pint, and we were talking some more and I decided to ask the hostess in England she was like we just had a cancel (8:00)of 4 the child was sick... so we took it and went back and cancelled our other ADR's at Le Cellier. We were not sure if they would charge us or not, but it was okay with both couples if they did. In the end we did not getting charged for the last minute cancellation.