Thread: Best translation
Quenya nosse means 'house, clan' and seems fine for 'family' (if not actually attested somewhere).
For 'friends' I think we need a plural [and I think melda is an adjective 'dear, beloved']. Meldor is attested but this might be masculine* as well, although I've seen modern mortals use meldor seemingly to refer to friends of any gender.
*Carl Hostetter once noted (with respect to an inscription from Tolkien):
'It appears that meldenya *'my friend' was altered by Tolkien from meldonya, probably to make it a specifically feminine form. '
For Sindarin I would guess *mellyn a noss
By the way, here's the citation that includes meldor...
In Q Eldameldor, S Elvellyn. That is, 'Elf-lovers'. The words Quendili, Eldandili (...), though not excluding affection and personal loyalties, would have implied also deep concern with all lore relative to the Elves, which was not necessarily included in the words meldor, mellyn 'lovers, friends'.
JRRT, notes to Quendi And Eldar, The War of the Jewels
To me this at least seems to imply that meldor may be used without reference to a specific gender, but even if not, I think this would be a relatively minor liberty with respect to Neo-elvish in general. I also found a reference to support that melda is an adjective (again I think you want a plural noun rather)
(In true Quenya the adjectival form 'dear' had the form melda).
JRRT, Words, Phrases And Passages, PE17