I've considered your theory in the past, with regard to Adam, but nothing in scripture supports the notion that Adam and Eve had children before the fall ( though they were most likely capable), but how then do you interpret Jude's statement in verses 6 and 7 of the short epistle by him? Jude suggests that the angels left their domain, the heavens, to go after strange flesh (not their kind.)
GINOLJC. estate is not a place or domain. according to Noah Webster's 1828 Dictionary of American English, Estate: ESTA'TE,n. [L. status, from sto, to stand. The roots stb, std and stg, have nearly the same signification, to set, to fix. It is probable that the L. sto is contracted from stad, as it forms steti.
1. In a general sense, fixedness;
a fixed condition; now generally written and pronounced state.
She cast us headlong from our high estate.
2.
Condition or circumstances of any person or thing, whether
high or low. Luke 1.
Jude 1:6 "And the angels which kept not their first estate, but left their own habitation, he hath reserved in everlasting chains under darkness unto the judgment of the great day". without getting into the definition of "Angel" here which might confuse you, I'll just considerate the word "estate".
looking at the definition above, it is a condition just like the first Adam. attention, Adam fell right .. but the question from where? off a cliff? or how about the back of a milk truck? no, he fell from grace with God. here fell, or fall is not physical act. just as estate here in Jude is not physical act.