I had a good look at Serendipity when two friends and I went in to do the east face of Table Mountain. Great looking ridge, probaby the most obvious "Climb me!" line on Owen. They went on to do the route the following week, while I went elsewhere. Here's what I know.
The approach route is reasonably well described in Rossiter's guide book or Ortenburger and Jackson's guide. It's a long approach to get to high camp in Valhalla Canyon. Anticipate a full day. We'd all been out there for more than a week and were pretty well acclimatized, which helped on all our approach times, but my friends said it was still a hump.
They didn't have route finding difficulties, at least in getting started on the ridge. I recall them saying they had a little trouble finding some of the specific features described in the guide they had (Ortenburger's) but nothing too serious.
I recommend you visit the climbing rangers at Jenny Lake. They can tell you about the stream crossing on Cascade Creek (is a log still there?), and they have some great photos of the mountain that show off the climbing routes and descents very well. Chances are good you'll talk with someone who's actually climbed the ridge. Also, early to mid-July is somewhat early in the season, so you'll want to get their assessment of snow conditions, etc. I saw the route in August, and the talus field leading up out of the canyon was free of snow then. I'm not sure what you find in July, but would assume there will be snow on part of the approach.
If you make camp in Valhalla Canyon, you'll have to descend the West ledges to pick up your gear. You might want to plan on a full day to exit. My friends did the whole affair in two days from the Climbers Ranch but they were wasted when they got back. Three days would be more relaxed.
Finally, the report was that the climbing was very good and the views excellent. Best of luck for your trip.