We'll most likely be there that week too. The festival is also a full-on regatta for the entire week so yes, I'm afraid there will definitely be a higher demand on boating facilities.
I agree with the posts above, best place to launch is
Mylor, which is free to use. It's a fairly shallow slip, good surface, pontoon alongside and probably usable at least 2-3 hrs either side of high tide?... They charge for trailer parking however. Not sure what the cost is as we keep the trailer back at our place.
If you want to keep the boat in the water there's an excellent marina at Mylor too, although I don't know what availability will be like that week. You've also got
Falmouth Marina,
Falmouth Yacht Haven and
Port Pendennis at Falmouth Docks.
Whereabouts are you staying?