Not to discourage, but the peak of the action at Pack Creek won't be until the afternoon on Aug. 25 due to the tides... is 2-ish hours really enough time to do it justice? If you depart by 9am, you'll be ashore by 10-ish. To be back in town by 1 or 2 means you'll be leaving by noon... That hardly leaves enough time to hike to the tower and back, let alone if anyone is already there (preventing you from access.)
Pack Creek is an amazing place to visit, but I've always thought it was an all day experience rather than a short excursion. When we were there the other day, nobody wanted to leave once a sow came to the creek to fish with her 2 new cubs... 6 bears fishing at once, and another 4 at the tower (plus 3 more down the beach on the boat-ride back to 5-Finger light!)
Happy Alaska Travels!