working backwards is a very good idea - that always keeps me out of trouble. i'd rather finish early and foil them in a cooler (they'll stay hot 3-4 hours that way) than try to pull them straight off the smoker.
If they're foiled, you could really let them sit for a little longer than just one hour before pulling. i generally like to pull mine as close to eatin' time as possible.
If you're going to start at 5AM, you might not want to put them back in the fridge at all if you rub them late enough in the evening. It'll take them probalby 2-3 hours to come up to room temp. Actually, I rarely have them out longer than an hour before I put them on - starting off with an internal temp of 50 or so ain't the end of the world. Mine seem to jump up to the 80-90's within the first hour or two. The problem is how long they'll get stuck in the 140's... sometimes they get stuck there for a couple of hours, sometimes not at all. That's really the big variable that I deal with. Luckily, very few of mine have ever actually plateau'd at that temp.
Now, just so happens that the last ones I did got stuck there for upwards of 3 hours, but I really had too many of them in my smoker (had 8 ten pounders jammed in there, 2 to a shelf) and they were extremely fatty cuts. Had so much fat dripped down into my smoker that I had to pressure wash it all out the next day. Two in an ECB isn't a big deal though, and I wouldn't expect you to have any problems.
If this is for a party make sure your portions are accounted for too - for pulled pork the yield is 50% meat when you're done, so if you have an 8lb'er you'll end up with 4lbs of pulled pork. Plan on 1/4lb per sandwich/serving - so if you have two 8lb'ers you'll end up with 8lbs of pulled pork that'll serve 8/.25, or roughly 32 people, one serving each.