Hmm. Kind of rock and a hard place. (I'm almost back home, btw, having just come from your neck of the woods with stop in Boston...)
You can low/slow a rib roast or do it as a high heat cook. At higher heat you will have more of a range of doneness, i.e., portions of the roast closest to the edges and ends will be more cooked than central portions. With a low/slow doneness is significantly more even throughout.
I am not often driven to cook two meats one above the other. Usually, if I do mix two, it's combos like chicken pieces and sausages or the like, not whole or large roasts. There are two main reasons for this: First, I make rubs specific to the meat(s) I'm cooking and the sauce(s) that will be accompaniments and do not like the flavored drippings from one affecting the other below; and second, I make decisions on how the cook is going, doneness and (if you'll forgive me), 'existential' questions based on both visual cues and smell, and the combo of two differently rubbed meats throws the olfactory cues into question. That said, I know that many combine cooks all the time and have no issue with it at all. But were it me, I'd likely cook the turkey on the kettle and the beef in the WSM (or vice versa, depending on sizes). Barring that possibility, I'd be inclined to cook one or the other in the oven. Barring
that, I'd likely cook the turkey first, immediately segue into the beef cook when the turkey was done (I'd do the beef at high heat in this case so as to keep the cook time shorter), and the beef would cook while the turkey rested, well wrapped to keep the heat up (the skin would soften but oh, well). Or, I'd do the turkey at high heat in the morning, segue to a low-heat beef cook after, rest the turkey 20 min or so, then probably prep the turkey for reheating by either removing the meat from the bones and cooling it (likely) or cutting up bone-in (less likely) and cooling. Just before the beef was done I'd reheat the turkey in the oven, panned with a stock-butter mix, covered, or I might package it in foil with the stock-butter mix and stick in the WSM to reheat under the beef during its last minutes of cooking and during its rest.
The jus issue: I cannot say that I am a huge fan of drippings-from-the-WSM-based sauces. Though a little added to a sauce might work out fine, I find the flavors don't work for me that well. I'm more likely to smoke or cook trimmings for a little while (rubbed) then remove them and add them to the sauces I'm making or to flavor a stock from which I'll build a sauce or two. I find that drippings that have been accumulating from the beginning of the cook are just too, well, potent for me, and not in a good way. For something like a beef rib roast where the trimming is often nil, I'll stick a a couple meaty neck bones (rubbed identically to the roast) on the lower rack and let them smoke and cook a little while but then extract them through the door and get them into what ever I've decided my sauce approach is going to be. I'm usually looking for good connection between the sauce and the roast but I want this based mostly on
beef with a minor rub connection and still less of a smoke connection.
For some ideas on the making of jus, see
here.