If you haven't already heard from Bill Sofer or Pres Martin you might
want to get in touch with them. While we used to assay the effects we
had on Adh expression in 3rd instar larvae, activity could be detected
in 1st instars.
As for recovery period, I would assume that those that survived
injection would need only enough time to recover from the wounding.
Another trick you might want to try is electroporation of plasmids into
embryos. V. Finnerty has a protocol for aldehyde oxidase.