This is a late answer, but in terms of inheritance: while with most different subraces, it comes to a flip of the coin essentially on which of the races the child takes after - this is explicitly not the case when it comes to both original Dark Elves and Drow.
When different sub-races of elves intermarried, there was an equal
chance for the child to inherit either of the parents' traits.
However, children born of the union between a drow and elf were far
more likely to inherit the drow traits, and were more likely to
parent a drow themselves. Dark elves possessed this traits
My citation here being the Forgotten Realms drow page,
Drow and in this case Dark Elf heritage, will be dominant over the wood elf in terms of abilities and appearance. Although that's not to say, there won't be any slight differences that would tip off to a different heritage, such as perhaps eye colour (the same wiki page, listing some differing eye colours as an indicator of some surface elf heritage somewhere in the bloodline).
But it's in fact so dominant, that Vhaeraun encourages his followers on the surface to take advantage of it:
He saw a general need for advancement for elves and encouraged cooperation, including intermarriage among the elven races. The goal included the subjugation of other races. Intermarrying also had an ulterior motive in the form of increasing drow numbers on the surface by taking advantage of the drow's genetic dominance
Source this time being his forgotten realm page, which itself provides several citations.
And as shown in the initial quotes: Dark elves share this "very genetically dominant trait".
So by far, the most likely outcome is essentially a dark elf baby with perhaps minor cosmetic such as eye colour differences.