Distance wont be a problem tbhHmm...
St Michaels Mount is a fair distance from Newquay, about an hour drive, road distance is about 35 miles.
Sunrise is probably the better option for shooting.
Sunset is not behind the mount, you need to move round past Marazion towards Perranuthnoe to get the best sunset angle, and even then the sun goes behind the headland at the western side of Mounts Bay.
There is a guide to Golitha Falls here.
I've never been there so I'm afraid I cannot help with details.
Going to make a day of itNewquay's great but quite a way from St Michael's Mount. Bedruthan Steps are close to Newquay though, and when you're down the south coast Kynance Cove is gorgeous