Good news!
I found a direct route from the spawn point to Serendipity Bay - takes about one hour to get there. After we realized yesterday that our new village is much further south than expected, it turned out today that Serendipity is located almost exactly east of the spawn point!
So, all you have to do is go east from Green Dog, cross the tundra and then a large forest (always going east). You will then see a big mountain range which you surround on the north side, slowly climbing up hill. Once on top you look down and see a lovely big lake, stretching from north to south. Go down to that lake and surround it on the north side. There you find some smaller settlements ("Nowhereville", "Northwoods", Wolf's Hollow" and others) and some altars of Vynora. Move east past the angry trolls, climb up a green hill - and there it is: the eastern coast! (This is where I just found Flinton's corpse!

WHAT HAPPENED, MATE?)
Now just move south on top of the mountain ridge, watch out for the spiders, and finally descend to Serendipity Bay!
I'm going to provide a crude map tomorrow - have to leave for a wedding now!
Watch out for various hostile creatures on your way: east of Green Dog there are large scorpions and goblins; I already mentioned the trolls on the north side of the big lake and the spiders near Serendipity - and you have the usual wolves, mountain lions, bears and rats, of course.
Take care!