en þá er (when)þeir eru frumvaxta,
fara land af landi ok þykkja þar mestháttar, sem þá koma þeir,
koma við þat út
(I couldn´t untangle the sense of this myself) ok þykkjask þá höfðingjum meiri.

but then they are (just) grown up and travel from country to country and (are) thought There most important.  As they come (back) home comes with this (with the thought??) that they consider themselves better than Chieftains

I have been thinking about this Alan after sending - I wonder if this could be a way of seeing

the translation

Koma við þat út could be - now it comes out - i.e. she is ranting on about the progress of the younger people I can only put it in modern English to illustrate this, so it will not be literal (which indeed I prefer

The travel from country (getting an education in a manner of speaking) and are thought in the other countries "there" to be most important 

"now it comes out -" can you visualizse this     koma við þat út      now it comes out -

she is in a fashion criticizing the parents for letting the youngsters have all this privilege

for after their gallivanting around   "now it comes out" that they have ideas - i.e. think themselves better than chieftains

I could wish I had done so much better with this, I shall copy up your translation again and go over this, as Uoden pointed out the word þvó  was completely new to me and at first I could not find in Zoega and completely misunderstood it

Any opinions of this phrase - koma við þat út      will be much appreciated she sounds (this Woman) too much like my Grandmother

Kveðja

Patricia