First of all, you`ll have a great time
I`ve been to Alaska last July and August and the first hike I thought of is the Harding Icefield trail (nearly have the same photo as Tonka...), it`s definitely worth it!
Down in Seward there`s also the lost lake trail, very beautiful or the trail to Caine`s Head.
Around Girdwood there are many nice short and longer hikes and I would recommend the Portage Pass trail starting at Whittier...
In these surroundings you`ll find many very cosy little camping grounds to stay at.
You can find all the hikes in here: http://www.amazon.com/Hiking-Alaska-2nd ... ing+alaska
And even more Kenai hikes in here: http://www.amazon.com/Explorers-Guide-H ... king+kenai
Concerning the kayaking, I did a trip, too, down at Miller`s Landing in Seward, beautiful view in Resurrection Bay and very nice guides!
If you have enough time, think of going to Wrangell-St. Elias-NP, it`s absolutely different and a great experience, too! (Although Kenai is still my favorite part of Alaska...).
(I`ll be back there next December and I`m already excited