I agree with other posts. Try to avoid beach launch unless tractor available and flat calm.
Mollers advice is sound. Helford river, especially if new to ribs is a great base for your boat. You could put in at Falmouth and make the short trip to helford, stick it on a mooring or at sailing club marina for the week. Your probably 20 min or so drive each day to your boat. If the weather is bad you can still tootle round the mouth of the river and find a sheltered beach to land your rib and have a barby!
Don't think there are any moorings at porthalllow?
Lots of safe trips (so long as you've local charts) out of helford. Falmouth, coverack, mevagissy, fowey, polperro. With dozens of secluded beaches in between.
We've dragged various boats the 300 miles, several times a year for donkeys! You're gonna have a great time!! Btw. If you want a hassle free holiday make sure your trailer (brakes & bearings) are in top fettle. We get our trailer serviced down there every year while the boat is off. I can recommend Lizard trailers but there are lots of other places. Then again, if anything does go wrong you'll not be short of people willing to help. It's a boaters paradise. Have fun!