Beaches are pretty good, you’ll probably want to go on the beach to the left of the marina as you’re looking out to sea. Wind is blowing ESE next weekend which, luckily for you, is the direction that’s likely to bring the best surf.
Llanbedrog will not be sheltered from the surf but it’s fairly shallow so the tide will go out a fair way. That said high tide is at about 1pm so you’ll be OK for depth wherever you go.
If you fancy eating out at all I’d recommend Dylans on the ‘beach’ in Criccieth and is only a short drive from where you’re staying.