Twin bilingualism

We are a multilingual family.  My husband is a native of Italy, and I am a native of California, and both of us speak English, Italian, and a good deal of French.  There are also two dialects in my husband's hometown, one of which he understands well (the Occitan language), and the other he understands perfectly and can also speak (the Piedmontese language).  I can understand bits of Piemontese, too, since it sounds like a mix of French and Italian, and can pick up a word or to of Occitan, but very little.

We speak English to each other, primarily because when we met I was not fluent in Italian and we've always lived in the US.  When the kids were getting close to speaking age, we were in Italy and I had become pretty fluent, so I got accustomed to speaking to them in Italian.  After seeing so many of our other bilingual friends' children refuse to speak their second language as they grew older, we decided we would try to only speak Italian with our kids.  And so far it's been a great success.  So great that they barely speak English at all, which is a totally unintended consequence of our actions.

I assumed that the moment they started preschool, they would be immersed in English and soon thereafter would start speaking English as their primary language outside the home.  I didn't take into account that, in addition to our many Italian-speaking friends, they also have each other to speak to constantly, even at school.  So they've been going to preschool 2-4 days per week since last July (not to mention weekly gymnastics class and playgroups) and are only now starting to speak some English.  Now, as in, last week.

It's pretty cool, hearing English phrases spontaneously pop out of their mouths.  And it's tempting, to me, to switch to speaking English with them.  I am fluent in Italian, but I do not speak like a native and my grammar is not anywhere near perfect.  I can't formulate really complex sentences, and my vocabulary is not bad, but it's very limited.  I know that my time speaking Italian with them is limited, and I am torn between wanting to be able to express myself better and teach them my own native language, and trying to preserve their Italian as long as possible, in the hopes it won't be lost.  I think we're lucky that with them being twins, they'll definitely maintain their Italian better than the other kids I've seen, since for the moment they still speak it with each other.  It's been an interesting experiment, and I hope we've done right by them.  I'm looking forward to seeing how they grow and learn even more.