Of course it's disappointing, but I think it's better to flag this trip away and plan another for you when your knee is properly healed. At only 8 weeks after surgery, you will still be in the very early stages. You'd need wheelchair assistance at airports, you'd have to take precautions against DVT on the long flights, and you wouldn't be able to do much walking around for sightseeing.
You'll probably still need to be taking some pain killers and you will need to rest, ice and elevate your leg.
My own surgeon allows short flights at 8 weeks, but he recommends not taking long flights until about 4 months.