Ask your vet for advice on what may be common in your area.
Clostridial disease is the main thing to vaccinate, best to read the British goat society's recommendations.
Usually the booster will be given shortly before kidding to protect the kids through colostrum, so is safe to use in pregnancy. Goats don't produce very good immunity so boosters should be given every 6 months not every 12 as for sheep, otherwise it is the same dose, same primary course etc.
The milk and meat withdrawal for heptavac and lambivac is 0, I believe other vaccines the same.
Your vet may be able to advise what is best, or other local goat keepers, or the person you got them from.
Hope that helps