Sure, you can do it either way. You are basically just heating them up again and finishing them off on site.
Grill searing would be best with ribs cooked slowly in the oven until tender done, transport cold, bring to room temp then sear with fresh sauce. That would be my choice, but I dont have a smoker I can lug around.
If you want to partially cook them in the oven and the meat is still dark PINK at the bone, I'd suggest using the hot smoker to finish them without bringing to room temp first. Use fresh sauce either way and don't save the 'juice' from the bags you transport them in.
The point is to make sure that htey are cooked completely. Pork should , and this is old school I know... but I am very old school when it comes to pork 'doneness'...always be cooked through with NO pink or ANY blood. All the juices should run clear, not bloody like rare beef. I would Never serve even a bit pink pork to anyone with immune system issues, young children or the elderly or anyone who has ever had bad food poisoning in the past.
Keeping the meat cold, check spoilage temps at the USDA food site for accuracy, between the fridge and the campsite is the key to spoilage issues. Once meat is cooked it should be cooled and refrigerated or frozen within one hour of it reaching room temperature to prevent spoilage. That's pretty standard. I am very conservative when it comes to any spoilage issue.
That many racks might be easier to handle on a smoker, but that depends on your equipment. Me, I am lazy. I'd opt for the searing on the flame grill. I'd also pour in a bunch of the sauce into the freezer bag and let them sit in that after they are cooked, toss out the sauce with the bags and and use fresh sauce while grilling.
I'd not freeze them then transport them as that can make the meat 'mushy' and tough. But I might cool, refrigerate until cold all the way through then pop into the freezer for at least an hour until slightly 'firm' then pack in cooler with ice. Wrap your cooler with a BLANKET and if you have one, a reflective surface wrap on top of that , shiny side OUT. I've had horrible messes driving for that many hours with food stuffs when the sun beats down through a window inthe back of the car or even in the truck bed. I am sure you know this already but just in case... it's a good bit of excess info to have. Keeps the cooler colder and the ice stays frozen longer.