Best stroller/car seat for toddler that falls asleep in the car

Okay, I am sure I am not alone in my question about the recurring problem of my toddler (well he's actually 3.5 now!) falling asleep in the car, and what to do about transporting him out of the car without waking him up. There have been countless times when this has happened (he falls asleep) and I need to run to the store for something, or even just get him into the house without waking him up.
or maybe head to a restaurant for a meal with family or friends. Ther is nothing worse than a crabby toddler, so I really hesitate to wake him up!

So far the only options I can think of are:

Get the Sit 'n Stroll car seat/stroller combo

Get a Britax car seat (Marathon, Roundabout, or Wizard - by the way, which one is the lightest of the three) and one of those GoGO kidz wheeled car seat carriers.

I am thinking the second is probably my best bet since he is already 3.5 and is 40 inches tall and 34 pounds.

Any other ideas on what would work?

I have hearad of some people using a McLaren stroller with a booster or convertable seat, but how safe is it and also how much weight and abuse can the McLaren's take?

Thanks much!

Beth

Maybe one of those $75 portable DVD players would keep your DH awake long enough to get to your destination? You can attach them the back of your headrest with a case that's sold separately. We bought our case at Costco. It's supposed to be for airline travel but works well in the car; it even kept the DVD player in place in our fender bender. Just a thought.