Hi kellib!
For sake of simplicity (and not overdosing on vitamins and minerals), I would recommend one of the 2:
1) prenatal only (extra calcium can be taken also, since the prenatal only has a percentage of your daily requirement)
2) multivitamin + folic acid (add the total folic acid in both and make sure it doesn't equal more than 1000 mg) + calcium (typically, your "nonpregnant" body will absorb up to 500 mg of calcium at a time, so space this one out later in the day; however, during pregnancy, the body stores a greater capacity of vitamins and minerals than normal, but it's always best to try to give your body a steady flow of good nutrition)
Both options probably provide enough B-12. With option 2 you could probably add it in safely, since it is a concern for vegan diets. I don't know off hand if there is an upper limit for this vitamin, above which you should not go.
As always, your ob/gyn is a good person to consult.
I'm looking forward to hearing good news from you in the future!
emily