Migraines are a problem for me, too, and Excedrin Migraine is not on the list of approved OTC meds. Thus far (knock on wood) I haven't had one, but you're right, caffeine would definitely be in order there!!
I drank diet Coke up until I found out I was pregnant with Timothy. Then I decided to be good and give it up. After I passed out in Walmart, my doctor told me that I could have 1 can or 1 small diet coke each day and it would be ok. It would actually help with my low blood pressure. So, I did, and Timothy turned out ok, my migraines never came back, and I didn't pass out again. Now that he's nursing, I'm still limiting my caffeine intake, but I don't know if I could give it up altogether. I try to drink my caffeine early in the morning, so it won't really affect Timothy's sleeping schedule (like he really has one!)
As to your parenting...I know you and Jonathan are going to be great parents. Most of it is trial and error, but kids are resilient and can handle a lot of mistakes by parents.