I found a line that I'd overlooked before. After Aldarion returned from that first voyage with Vëantur, it states:

Vëantur did not again voyage from Númenor; but the Númerrámar he gave in gift to Aldarion.

So you were right too. I had totally forgotten that Vëantur had given the Númerrámar to Aldarion. The building of the Eämbar (btw UT's index says that [the] name doubtless means 'Sea-dwelling') came sometime after Aldarion's thirty-ninth year, and the Palarran came later.