Wow! So much to consider.

Firstly, you will make colostrum for the new baby even if you keep feeding the toddler. Some people have milk all through pg and get colostrum at the end and some get colostrum quite early. Your boobs are very smart, and will make milk for the newborn, although evidence suggests the toddlers saliva can alter the milk production when they feed.

As for cycles and feeding, everyone I know got their period back before 12 months while feeding. I was the exception but I fell pg while still feeding 6 times a day and dd was 18 months. You don't need to wean to get your cycles back necessarily...by 12 mths their food intake is enough to rest your bbs and stimulate ovulation.

As for fert meds and feeding...double check this with the aba because I know there is conflicting advice depending on the drugs.

Good luck and you never know...you may get lucky without even thinking about it!!!!