A couple things you need to know about ribs and rib racks:
When I use rib racks I like to leave one space empty between the slabs so that the smoke and heat can flow evenly over the surfaces. This reduces cooking time while allowing you to smoke at the same temp you would normally use. If you don't leave a gap, the slabs will act somewhat like a bigger cut of meat and take far longer to smoke at the same temp as you normally would use, so higher temps are in order in that case (I've done it both ways)...say 260-270* instead of 225*.
As for foiling, you can pop the racks into a large baking pan, then, build a foil tent over the racks and continue with the steaming phase. For open grate final phase, just remove the foil and set the racks back on open grates. When you pull 'em out to serve, just place the racks back on the baking pan as you remove them from the smoker grate.
I don't remove the slabs from the racks to slice until after they've been out for 5-10 minutes for a brief rest period, otherwise they seem to leterally break apart. They tend to put a love-bite on the rib rack wire frame, so just work 'em slow and easy with tongs, insulated neoprene gloved hands, whatever you have to work with...I usually cover them back up with foil to keep warm after bringing them out of the smoker while they rest.
Obviously, basting or mopping would be a bit more of a challenge than when the slabs are laying flat...never have felt the need to do it to ribs myself, so I'd have to think about that for a minute or three.
Ah, man, I love to cook for reunions and other gatherings...have a great time with your family!