I’d be pissed, as parents they should not have let him anywhere near your couches especially with chocolate. I take food places with my DCs but I’d never give them chocolate in someone else’s house unless I asked it if was ok and they were sat at a table. It was the parents who allowed the child off the table and weren’t prepared with wipes to clean him as soon as he was about to touch something.
Good friends don’t do this so I’d have no problem sending them a bill for cleaning.
I have cream couches. Pre covid when we would have kids round the sitting room was out of bounds, this was made clear to both parents and kids with the fact I had a gate up to stop the kids going in there. My own kids fine, they knew the rules on food and I actually don’t mind cleaning my own kids shit up. Other people’s kids though are a different kettle of fish, especially when the parents don’t discipline or watch them. One kid threw a £140 remote control robot of my husbands down the stairs, just to see what it would do, his mother never said a word, needless to say he was never invited back. And that also put a stop to kids playing upstairs. There was another time we were having a party, lots of kids, no one was allowed in the sitting room, gate was up, lights off, the sitting room not only had my cream couches but also fragile and irreplaceable items my own DCs know to be careful around. One girl about 9 goes in and picks up a very fragile ornament and starts pulling at bits of it waving it in the air, monetary value zero, personal vale irreplaceable as it was a gift I’d bought my grandmother as a child and I was given it when she died. I told her no kids in here the party was in the back of the house, but she ignored me and she still kept trying to touch things, she made a beeline for my dads ashes so I told her that was my DCs grandad in there, they burnt his dead body and put some of the ashes in there, she shit herself and left the room. Her dad stood there the whole time in the doorway and said, this is why we don’t have anything nice in our house they break stuff all the time. I felt like telling him maybe he should actually do some parenting then.