@seekertruth72 I think “teaching them” will be difficult, if you are speaking to then in English 90% of the time and the remaining 10% becomes an (often frustrating) teachable moment.
Most of us here believe in One Parent, One Language - meaning you do not actively
teach but rather, to your kid, you do not speak any English at all. There is no reason for them to start to communicate to you in Italian when they are used to speaking to you in English and they know it works well.
I would probably try to ease into it. Use simple words with sign language, when you hand them something say the word for it in Italian. Use Italian for every single repetitive task “put on your shoes”, “put your plate in the sink” etc with a show-and-tell, no English. Use English as little as possible to translate yourself, slowly ease into using Italian exclusively.
Switch out their TV and book materials for Italian ones. Make sure they are always hearing Italian one way or the other. Face time those grandparents often.
It can definitely be done but speaking English to them by default with an hour study session of Italian every week will get you nowhere I’m afraid. They are not too old to pick it up quickly. I have nieces and nephews that moved at this age and they were fluent after a couple of months with a LOT of exposure.