HPN is definitely worth looking at. It's very convenient to CT and an easy airport to pick up or drop off someone, although I don't think CT Limo runs there (not positive). I think it's no more than 15-20 miles from Darien. One small caveat about HPN: fares can be higher and you'll need to make a connection from most other cities (direct flights from ORD and IAD on UA). I'd also say that the airport can be a little backed up during the holidays and traffic can be congested around Stamford during rush hour, but probably still better than LGA.

Again, the big upside in my mind is that it's really easy to get in and out of. (Similar to Tweed in that respect.)