Steve, this is what I'd do: put the two larger ones on the bottom rack (pushed toward the center with little space between) and the three smaller ones on the top rack. Regarding which of the top three to probe, take into account the thickness as well as the weight of each. On my 18.5" wsm, I can usually position both my bottom rack pork butts where I can reach the bone to check with tongs, and still be able to top off the water pan. Lay all on the grate fat down, thicker sides to the outside, and I wouldn't mess with 'em until checking for doneness the next day.
Regarding times/temps, the best thing about cooking bbq overnight is that it's not critical since you can keep 'em hot for several hours in a pre-heated cooler, depending on quality and other factors. I'll add a couple of 2 liter bottles filled with hot tap water if I need the meat to rest most of the day. After wrapping the meat in foil and putting in the cooker, I fill in the spaces with wadded up newspaper.
Since you're not eating til supper, and assuming you don't want to stay up past midnight, go low-n-slow, or 225-250, and allow about 2hr/lb just in case you need it.
That's not a lot of meat for a big 22.5" wsm at all. When doing a long cook, what becomes as important as knowing your cooker is knowing your particular charcoal choice.
