What Should I Do with My Remaining Frozen Embryos?

We’re in the process of deciding what to do with our remaining embryos. While I know you can’t tell me if I want more kids, there are practical questions I am still curious about. If I opt to implant another, I would like to do it in the next few months (for arbitrary age mindset reasons). That said, I wanted to nurse my 18-month-old until he’s 2 (also arbitrary, due to a sense of fairness, since I did that with my older kid).

So here are my questions: (1) Are there drugs in the frozen embryo transfer process that would legitimately interfere with breastfeeding? (2) Would breastfeeding, given my period has been back for 12 months, lower my chances of successful implantation? And (3) if I do have to defer implantation, is there any reason for me to stick to my “I don’t want to be pregnant after 40,” given they are eggs from a younger age?
—Two on Ice

I appreciate your pre-empting my speech about how I cannot tell you how many kids to have!

The drugs that are typically used in these cycles could affect your breast milk supply. However, considering how far along you are in breastfeeding, the effects are likely to be small. It will certainly be recommended that you stop breastfeeding, though, just because we do not have much data about this situation. I realize this is not a very compelling answer.
We can extrapolate the answer to this question from the question of getting pregnant while nursing in general. In general, breastfeeding acts as birth control by preventing ovulation. Breastfeeding is not contraindicated during pregnancy, including early pregnancy (i.e. implantation). So this is fine.
No. In the immortal words of Matthew McConaughey in Dazed and Confused: “That’s what I love about these high school girls [read here: frozen embryos], man. I get older, they stay the same age.” You’ve got a little breathing room.