hun it sounds like you have a GREAT plan on how you want things to go and having an OB that supports you is wonderful news, i hope everything goes as smoothly as possible for you in that regard.

In regards to not knowing if your ready, i can tell you 100% i've been there, therer was 15mth b/w DD1 & 2 and there were moments during my PG that i thought there was no chance in hell i would survive with 2 kids under 2.
It's a rational 'fear' and not something you should feel bad for.

I must say though for me it was easier than i had thought it was going to be, DD1 was really quite good with her sister and a lot gentler with her than i ever thought, she too is an adventurer and has unfortunately taught her sister all her tricks (no oven stuffing though ) try and think of the positives where you can.
When your trying to get something done he has someone else to keep him occupied, having a sibling really is a wonderful thing for little kids, they learn and grow together.

You will do an AMAZING job, think positive and remember your a MUM, we can do anything