We’re sitting on it for two days before we tell them.
Ireland is a much better choice than Sicily if you have kids. Sicily is mostly of interest for its History, which would likely bore the little ones to death. Ireland is more beautiful and the people are a lot friendlier.
The wedding I mentioned earlier was a marriage between a Sicilian man and an Irish woman. Imagine a reception evenly split between the most endearingly offensive people in the world and the most easily offended people in the world. I spent the evening hanging out with the offensive (but friendly) ones.
They were thankful we provided an alternative. It looks like most likely 2 weeks in Ireland/Scotland in 2028.
FIL seems to want to go to Australia, I’m not sure how much traction that will get, but it could be fun too.
So, my take on this is that your sister in law wants to introduce her daughter to her Sicilian relatives on the occasion on that daughter’s second birthday. To these relatives you are a distant in law, in whom they have no reason to take an interest, and with whom they can only communicate with difficulty if at all. Would that be an accurate description?
No, there are no relatives in Sicily we’re visiting. I think my SIL just wanted to see where her family came from.
Anyway, we turned it down and proposed a 2028 trip to somewhere else. This gives us a longer time to prepare.
We had just spent a fortune on a European tour that we incurred the full cost for four people instead of just our two. So financial, not ruined, but need to be economical for a year or two. Two months later …
Oldest: Hey you know that family cruise we were talking about?
Us: You mean the one in 3 to 4 years?
Oldest: Yeah I bought the tickets. All you guys need to do is pay the airfare (for 5 people).
Yikes. Yeah, these things really need to be discussed ahead of time. Did you end up going?
It’s going to be an expensive trip, especially because any time my husband misses from work is not financially compensated, as he is paid per session. So we have to save up the cost of the trip plus the lost income.
It’s a lot to set aside monthly, but a lot easier to come up with by 2028 than May 2026.
It feels a bit like an extravagance, but if we waited for the perfect financial situation, I don’t think we’d ever go. It’s just a matter of adjusting priorities.
Had to. And as it turned out, it was all because his wife wanted a cruise so of course we all had to go.
I fully agree with this.
I was with my family in the Val d’Aosta (extreme northwestern Italy) a few weeks ago. The region is officially bilingual (Italian and French). I speak French and understand Italian (courtesy French, grandmother, and food). Despite that, almost everyone spoke to me in English. I know they are doing it to be helpful, but in my opinion it dilutes the experience.
In any case, lack of Italian (or to be more specific Sicilian) language skills really should not be a concern.
That aside, I think @Spice_Weasel is making the correct choice and Ireland is the better way to go for all the reasons mentioned (by the way, don’t assume communication will be easy over there either 
)
Australia is a very long flight - 15 hours from LA to Sydney. I’d certainly not take any 6-7 year old there unless they’d already proven they can handle a 5-6 hour flight with no issues - given your son’s challenges I’d really recommend against it. Honestly, you need to not let FIL drive anything in your destination selection, especially given things like this: