How to help friend with dying pet

Hi reddit, sorry for any spelling/formatting mistakes I’m currently on mobile. One of my friends has had a dog they’ve had since their formative years, and its around 12-13 now I’d say. The dogs age is catching up to it and it hasn’t been doing too well for the past year, and its condition is gradually getting worse. My friend took their dog to the vet a couple weeks ago and the vet told them to consider putting the dog down. In the past couple of days their dogs condition has taken a turn for the worse. I haven’t this to my friend, but I fear that their dog may die soon. My friend has gotten really depressed about their dogs condition and I’m not really sure what to do or say. I feel like it’s just a terrible situation and all I can think of is “I’m sorry”.

Is there anything I can do for them? How can I comfort/help them? Is there anything I can say? We were supposed to go to a convention in a couple of weeks that they were really excited about before, but now they (understandably) don’t feel like going. If they don’t want to go I will not push it, but would it be better to have them go to the con with me than just sit home? I’m thinking that if they were to go out and do something it might help them, but I don’t know. Any advice would be appreciated, thanks.

EDIT: I’ve also been thinking about suggesting holding a funeral/memorial for the dog as a way to remember it, but I’m not sure if that would be insensitive? Just to be clear I don’t mean it as a joke or anything, I think holding a funeral may help them grieve.