What about rigor mortis if you leave them sitting up in a seat?? Laying out, perhaps in a modifed form to the method used in hospital would be preferable, wouldn't it? Even tho they are dead, they need to be shown some respect, and leaving them sitting up in a seat pretending they're alive doesn't seem to do that. I'm not sure what you'd do with them then of course...difficult in a confined space.
Doing CPR for 3 hours would be incredibly difficult - hope you're very fit!!
M.