Have your goats been vaccinated with Lambivac or Heptavac before (double dose?), if yes a booster anbout 4 to 6 weeks before kidding is all hat's needed (and from then on every 6 months or so).
If they haven't (or you don't know) I am not sure what the best way forward would be, as they need two doses 4 to 6 apart to become immune in the first place (same as sheep).
If they have been done before, just do both of them asap for their before-kidding-booster.