When looking at a trip to the Kenai Pennisula you need to ask yourself what your expectations are. If you have no problem sitting in a boat all day for 1-3 bites maybe land a King or two, but the chance to land a 30-40 lber go Kenai. If you time your trip for mid to end of July you should hit plenty of Reds on the Kenai too. The legendary Kings of 60+ lbs are rare anymore. The Kasilof in July is typically slower fishing but less crowded. If you want Halibut, rockfish, Lings, silvers and don't mind long runs to the grounds go to Seward end of July through Sept. If you want great halibut fishing shorter runs and maybe some salmon Homer hands down.
The best guide on the Kenai I have fished next to is Greg Brush, never needed a guide have our own boat. Stand up guide and a great fisherman.
If you aren't stuck on going to the Peninsula in July I would recommend Fishing some of the Mat Su Valley streams in August. Great Silver fishing from the shore and world class rainbow fishing.
Good Luck