You're on the right track.....
Keep the temp up higher like you're planning, it will then get a cripiness to the skin that you can't get at lower temps....
If you want to make gravy, don't use water in your pan, start with chicken stock, the flavor isn't affected very much & it will create a good base to go from.....
Edit: This next part is for doing the turkey right down IN THE PAN ~~~>
( I read back over this & thought it might not be too clear...)I don't have any pics, 'cause I haven't done this in a few years, due to the wife & others' wanting to do things "their" way, but for years, I've used an old steel pan (no plastic or rubber handles)& set it down on the charcoal grate, with coals all around.....
Wrap the wingtips & leg ends w/ foil to prevent burning, also a foil strip around the front of the breast at the lip of the pan up about two or so inches, to protect from the higher heat.....
Set on celery stalks (across the short way in the pan, to raise it up a bit off the bottom) & fill the pan up most of the way w/ chicken stock & spices....re-fill as it cooks down....
Smoke wood or not, your choice....Apple goes real good, or cherry, but too much cherry will turn things dark if you over-do it......
If you cook right in the pan, it's almost a given that it can't dry out; only way that can happen is if you go too long & the top of the breast may start to dry....
I'll almost always inject, Tony Charere's Creole butter is a real good one, or some of the different Cajun Injector brand flavors, depending on how your tastes run....
If injecting, there's pretty good directions in the packing, just try to spend a little time & get it thoroughly shot thru....
It's maybe just a hair faster than the equivalent hrs./ per lb. in the oven, but that will give you a general guideline to go by.....
Weber, World's Greatest Outdoor Oven, by FAR !!!!
If on the grate or down in the pan, tent w/ foil late in the cook IF it's getting too dark of a skin.
That will slow down the browning a huge amont, if it's just a fairly loose tent, it's quick & easy to check where you're at......
Some folks will cut up apples & oranges & load the cavity to flavor some from the inside, works good....
I hope these ideas help, keep asking, if something seems not right....
See Here also ~~~>?
http://weberkettleclub.com/forums/food-pr0n/my-first-turkey-on-the-kettle/