The cam column is repairable and you can probably stabilize the other crack as well. In this high stress area I've found only two epoxies that work -- 3M ScotchWeld DP 8010 (and its variant 8010 NS) and Loctite 3030. I've tried the G-Flex and it doesn't take much to pop it loose. Here are my results with Hobie's Polyethylene:viewtopic.php?f=11&t=12550
I like Bob's suggestion of making a repair sandwich of PVC halves, filled with epoxy to quickly and neatly apply the mix, as time is of the essence! -- haven't tried it though persoanlly. All your repairs will be inside the hull where you may not be able to see and work at the same time, so good planning cannot be over emphasized and working with sequential small batches prevents premature set-up. Don't skimp on the material -- it has to absorb the structural stress load where the PE failed. It's also a good idea to so both sides -- if one side is cracked, the other is probably not far behind.
Take a look at these notes from past repairs and don't hesitate to ask if you have any questions:viewtopic.php?f=71&t=33359&p=134475&hilit=#p134475viewtopic.php?f=71&t=33359&p=134482&hilit=#p134482viewtopic.php?f=11&t=11245&p=59882&hilit=d#p59882