You are right. But one item I failed to mention is that we are taking the Spirit Airlines flight that arrives at Logan at 5:50am. Assuming the short night's sleep doesn't kill us, we at least get a very early start. The more I thought about, Newport is not possible. Another our and a half just to drive there and back. So here's what I'm thinking.

We are out of Logan by 7am, in Providence by 8:30. In Providence, say 2 hours. Headed to Cabot, VT by 11am. Should make it by 4 at least. Tours go till 5pm. After that, we have no schedule, so whenever we get to Littleton is not a problem. We are late nighters.

I think we can do it, but you are right, we will have to keep an eye on the time. If it doesn't go that well, we will skip Cabot and drive straight to Littleton.