Cafe at Whistling Sands (Porthor) is worth a visit, they do a good breakfast and it’s a lovely beach.
Ty Coch for a beer on the beach obviously. For food, the best option nearby for a meal out is The Ship in Edern (next village South of Morfa) but you need to call up in advance as their capacity depends on the weather (they have outside bits in good weather). The Cliffs in Morfa is a bit hit and miss. Gwen’s chippy in Morfa is actually pretty good as it’s all cooked fresh.
The garage in Morfa is a bit of an Aladdin’s cave and has a really good butchers/bakery area at the back if you need to stock up for a BBQ.
Wander along to the Brewery in Nefyn https://cwrwllyn.cymru/en/ – great local beer.
They do surf and SUP lessons at Nefyn.
For biking, there is a crazy downhill track at Nant Gwrtheyrn but be careful… The cafe at the bottom is not bad. Walking in the Rivals is good, on a clear day you can see all the way down the peninsula and across Cardigan bay to Snowdonia.
You can cycle up the hill behind Nefyn which is mostly fire road with some small sections of singletrack at the top. Coed Y Brenin is about an hours drive.
Porth Ceiriad is good for a surf or just for a nice beach walk that’s a bit quieter.