If I were you, I would try to get there before 10 AM. The river release begins at 10. There is usually a line of outfitters waiting to get on the river by then. The parking lots will also be full of their buses and customers. As a raft guide from Maine, I'm sure you're familiar with the customer scrum at the put ins. It's not so bad if you have a paddle raft and some folks to help you, but it's very difficult to get an oar rig through the customer line.
I usually try to get to the put in between 815 and 845 am. The outfitters usually start showing up around 9 AM to blow up their boats. The buses with the customers usually start showing up about 930. 815-845 am gives me time to drag the boat down the hill to the put in. I usually leave my boat right on the river tied up out of the way. After that, I have enough time to set shuttle and be back before the release begins at 10 AM. Once the release begins and the pond floods, I usually paddle across to the small island to stay out of the way of the commercial companies until I feel like setting off down the river.
There are a few rough campsites on the put in road. Drive past the put in itself a ways and you should see two or three of them on the right.
I might be able to get together with you on that day, it's a little early to tell though. Depends on what my work schedule ends up being at that time.