Ultimately OP, you know your guests better than we do. Especially if there are only 40 of them. Can't you sound them out rather than sounding us out?
Start by talking to the people whose presence is most important to you, such as your immediate family and anyone you would have as a bridesmaid or best man. Are they up for it? If yes, how would you feel if they were the only people there? Would that still be a good wedding for you, or would you feel sad if other people couldn't make it?
If you get positive responses from the most important people then maybe start sounding out the rest of your intended guests.
As others have said, do bear in mind that people's circumstances might change and you may end up with some people who say they're up for it now not being able to make it in three years' time due to pregnancies, children, changed financial circumstances etc.
But in general you will get a lot of very negative comments about having your wedding abroad on Mumsnet, when this may not actually reflect the feelings of the people you intend to invite. You know them better than we do.
My best friend, for example, says she loves abroad weddings, having been to weddings in France, Spain and Greece and was really sorry to miss one in Italy because it clashed with the one in Spain. I personally enjoy weddings outside the UK much more than weddings in the UK because in the UK it's virtually impossible to find a venue which doesn't force you to have a cash bar and chuck all your guests out no later than the stroke of midnight, whereas the weddings I've been to in other European countries have better food, more and better wine, and the party has gone on for longer. That's not the fault of any of the couples whose weddings we've been to in the UK, it's just that the rules around the wedding industry in the UK are a bit shit. That's ultimately why we decided not to get married in the UK.
So if your friends and family are up for it, I reckon you'll have a much nicer wedding in Tuscany.