I dont know if it still exists, but there used to be an association where people could join up to get cheaper flights to and from Australia ,after belonging for a year. It might be something you could check up on. If it costs very little to join, you could join now so that by the time they actually get moved out to Australia it would not even be a year until you could go to visit them.
Whilst it might be a really useful thing to do , the reality is not the point, but by checking this out you find out the actual situation, but you are then showing your son that whilst you are sad for yourselves, you accept their choice and are making some concrete plans to see them in the future. That would also cover your husbands attitude at the moment, as you could go alone or hopefully by the time it was something you wanted to use he might have changed his mind and be happy to go too. If anyone on gransnet has done this they may be able to give you some tips. Then I agree that a very long straight through flight is hard anyway and even more as we get older. So if you factor in staying perhaps for two nights somewhere on the way, you could look at this other little holiday as a possibility that you had not thought of going to before.
This could change on every trip you make so that you get to see other places too as a sort of "extra". I have lived abroad and travelled a great deal, and whilst it is of course not true of Australia, I used to say to my family that for example, when I lived in Portugal, they could come by plane to see me and be there much quicker than if I had gone to live in the Outer Hebrides , which had been a possibility. So perhaps you could think of places your husband had spoken about wanting to see, or rather sneakily an occasion he would like to visit. So is there a Golf tournament, or a motor race or a horse race he would have loved to go to? You could maybe check them out and suggest that you travel at about that time so that he could do that as well, rather than it being an extravagant one off trip? Of course you could also choose something that you have always wanted to go to and say how lovely it is that you will also be able to do that on your trip, and of course suddenly think of how he could go to something too. It just might help to balance against the awful despair he is feeling.
I hope that these might be some help to you and set you off in ideas of your own. They will still be your family wherever they are in the world, and no one knows how the future will go. After lots of travel , my family returned to the uk, and so we were around to see my parents etc. but naturally you find when you are reasonably local , you dont make those actual concrete plans to meet up in the same way, so you may actually see as much of them in time just that it will now be more concentrated and deliberate. Wishing you all the best and that these messages from gn's give you some comfort and ideas for the future.