Sorry but you are being unreasonable, they invited you and you refused.
The situation has changed so much since they booked, so you really shouldn’t be going anyway, like others I’m surprised that they are still going.
You have been visited by your family, this is also something that shouldn’t have happened given your age and health problems.
Please don’t begrudge them their time away, it might be their last for a long time.
Look after yourself and try not get bitter about it, these are extraordinary times and many GNers aren’t able to see their family at all.