You've gotten some really good advice already.
I almost fell off my chair when I saw you were thinking about icing it down in a cooler though.
With very little extra effort and to really knock your party out of the park. You could do a chuck roast and a pork butt for a bit of variety .
Pork Butts are really easy to do and are my personal favorite.
I second the idea to use Jeff's rub. Its easy to make and is a killer rub.
You really don't need to check every hour In fact the less you peek the quicker and in my opinion the better your smoke will go. The main thing is to get the temperatures right at rack level in your smoker. A remote Probe in the meat is a huge plus. If you don't have a remote you can get one of those cheap meat probes stick it so the tip is as close to the center of the meat as possible and not touching a bone. Then check it visually near when the meat should be done.
Keep the smoke thin and blue and you should be fine. Hope your party is a success.
PS. With the planned use of a cooler to keep things HOT You can start your smoke a few hours earlier giving yourself at least 2-3 hours of leeway on the finish time. This is a good idea because sometimes meat just plain doesn't co-operate and will run 2 or 3 hours late on you. By starting way early you eliminate the possibility of having your guests wait too long to get fed. A roast will stay hot for an amazingly long time wrapped in a couple layers of tinfoil and then a couple of towels placed in a cooler. Someone already mentioned that the meat Needs to rest
to help in the tenderization process. Very true. In my opinion the longer its in the cooler resting the better. An absolute minimum of 30 minutes is needed for the juices to settle down and the connective tissue to dissolve into pure flavour.