There's some good info here. And yes, get the maps.
Other things to consider: the weather is better later in summer, up to the middle of September. However, whenever you go, plan on wet. Even if you don't have actual rain, the morning dew and local precip will be wet and cold. Also, layer up, it may be in the 40's in the morning and in the 80's in the afternoon.
Traffic is heavy with all the tourists during the summer months but drops off significantly after Labor Day. I too recommend on riding north to south because of the wider shoulders--but no guarantee on the winds being favorable tho--they blow in all directions.
PALux makes a good point--the maps lie about the elevation gains. Little know Oregon secret: elevation depends on the time of day and distance ridden--hills get bigger as the day wears on.
Camping: the state has hiker/biker sites at most of the state parks for a fairly reasonable rate (I think it was $4 last year) per biker--but the sites are usually only so-so. If you buddy with some other riders and get a regular site you'll probably have more room and possibly a better view (if there is any). Too, many of the state parks have yurts and now small cabins for a pretty reasonable rate. You can't reserve hike/bike sites, but you can yurt/cabins--online.
Some of the best scenery and neat out-of-the-way places aren't on the maps. Sometimes poking down a side road, asking the locals, that sort of thing will result in views or even parks and campgrounds not even listed on the maps. I've seen so many bikes pass the Umpqua River lighthouse/Winchester Bay loop and miss out on some of the most spectacular scenery on the coast. Plus if you're going south the hill just south of Winchester Bay is a long pull. You mostly miss it by going around.
Other pearls of wisdom here: the north coast (north of Newport) is more heavily populated therefore there's more places to eat, buy supplies, get water--that sort of thing. South of Newport it gets a little more spotty. South of Coos Bay it can be downright sparse at times. For example, there's nothing between (about 30 miles) from Charleston/Coos Bay to Bandon (there is a state park just north of town--but the closest store is another 3 miles). And south of Bandon the towns are about 30 miles apart and not a lot in between. None of this is a problem unless you're self supporting.
I'd suggest writing the local tourist bureaus--they'll have local maps and info as well. Oh, and when you get to Langlois, stop at the store and get one of their hot dogs--about 1/4 pound, homemade hot sweet mustard, crunchy dill(!) pickles--oh man, they're worth the trip alone.
John in Roseburg