After reading all your responses, and <aghem> discussing (translation 'having a big fight') with my hubby

, we have decided to take the 1 week, Tuesday to Tuesday vacation, simply because it offered us the direct flights. Actually, it took dh talking to his Mom

last night, who is from England and travelled a lot with him and his siblings when they were young (taking them across the pond to visit family), to admit that perhaps direct flights with young kids were more important than an extra couple of days!
Besides, I know my kids - they will be completely gung ho for probably the first 4 days, then slowly begin to burn out - by the end of 7 days, we will all be longing for our own house, our own beds, our own toys, etc...
Thanks everyone for all the responses - next trip will definitely be longer with some side trips to SW and possibly
Legoland, the ocean (since Dk's have never seen the ocean yet!!) etc... For our first trip, we are keeping things lowkey, but in 1 or 2 years - look out California, here we come!! The baby will be older, we will need fewer carseats (can't reconcile hauling 3 carseats!!!), and Ds2 will be old enough to remember more as well.
I am so excited - dh is booking flights this morning, and I will be booking the package tomorrow, either thru our TA from AAA (who is not so good at getting back to me, so she has a very small window to get in touch) or by myself through the AAA website.