This is a very generic question. Which will probably explain the lack of responses. You really need to give more background to the situation. What would their financial situations be, how many years would they have lived in Italy as minors by the time they are 18 etc.
The best thing you can do is go to your local Italian consulate and ask for advice. Unless any Americans on here have other knowledge to share?
Other factors that come into play here include what sort of visa/residence permit you and your family members have, your financial resources (mainly where they come from - say, pensions or personal savings, or other), would you become eligible to apply for Italian citizenship at some point (before they turn 18), would they attend university or other higher education in Italy? etc.