Any recommendations of the route. Will be arriving at 3pm, Sat., 10 October 2015.

Go over the causeway towards Marigot. Go by Grand Case. Veer to the right at the round about. Proceed to Orient Beach and you'll be there.

Take a cab and relax. You will thereby avoid time spent securing rental car and other nonsense. You will need it, flying all day is tough.
You can purchase enough provisions for the night at the little Orient store.
The next day you can rent a car right on site at Club O. (It will cost about more than going with one of the traditional airport options but not much more.)
And there are grocery stores nearby to stock up for the week, but again, it will be the next day so you'll be up for it.

We stay at LaPlage..and find either way to Orient just as fast as the other. I wouldn't waste money though taking a cab to Club O. If you are planning a car, get one at the airport and it will be much cheaper than a round trip cab ride from airport to Club O. The rental of the car will be about half of the cost of going back and forth by cab. It's an easy ride from airport to Club O...

If you need to stop for provisions, there's a chance their store will be closed by the time you get there. Either stop along the way or pre-order from the website so everything will be in your unit when you arrive.

There is a Grand Marche right next to the causeway after you cross it. It will be open when you arrive. Just leave someone in your rental car with your luggage as you shop. Very convenient.

Thanks for all the advice. I already have a car ($106 from Alamo for the week). I'm glad to know about the online ordering too. I remember driving there in the past but wasn't sure of construction, bridge, etc.
It's been two years - really looking forward to it.

Another great option, used by many here.

https://www.shopndropgrocerysxm.com/

I believe the causeway through Marrigot is faster on the way to Orient but not so much in reverse. I always take the road to the marina and the ocean side route on the way back. Agree with SXMScubaman don't ever leave your rental car with your bags or anything valuable in it.