Marianne,
I used to be a live in nanny for some very successful people. Now I am a mother of three and I know EXACTLY what you mean. I changed jobs from a real successful career to be able to stay home with my children so as to not put them in daycare. To be able to sleep in (and not get up at 5:00am like my husband does), to be able to nap regularly, to not get so many cold/flu bugs and remain healthy. It is very stressful, tiring, aggrevating at times, but well worth it. I don't think my families I nannied for had any less joys with their children than I do mine. It isn't a matter of 24/7 all day, every day, being a mom and staying with them every minute so they don't run amuck and become hoodlums (according to some other listers who must not have children!); it is definately a matter of quality time vs quanity time. The children I nannied have always had nannies from the time they were born. The eldest just graduated from Stanford top of the class after interning with a past presidential candidate and the other is at Yale (again top of the class). They both were active in sports and are very intelligent and friendly. Their parents spent quality time reading to them at night (every night), helping them with homework, vacationing with them often, going to their sporting events, etc while going to work and being very active in DC politics/governmental issues.
Anyway...spend some time finding a care provider. Even starting now-9 months out. I suggest going to Annapolis or DC to use their agencies to find someone from the state or even out of state (since you will be providing room and board) that is right for your children (no matter how many you plan to have!). I wish you all the best and I am sure (no matter what they naysayers think!) they will turn out to be just what you always wanted!