2 be or not to be 3, that is the question

The current kid situation around our house is that we have Emma, 5, living with us 1/2 of the time and Miles, 10 months. We've been pondering whether or not to have a third child, and it's not an easy decision to make. On the one hand I'd really love for Miles to have a constant companion at home and I can already see the sadness on his face when he waves bye-bye to his big sister at dad's house. But, on the other hand, a third child means a LOT more work for me. AND N has taken a new job that requires a lot more travel and he will probably continue to have jobs with lots of travel in the future (just the nature of the biz he's in). So, what to do? There are so many great things about having a big family with lots of kids around - lots of action constantly, always someone to play with, lots of friends around eventually, warmth, joy and fun. But, am I up to the task? I really wonder this - am I cut out for raising so many kids?? I wonder. I love being a parent, I really do, but I also want to do other things too. I want alone time with my husband every now and again and I want alone time for myself. Actually, I don't want it, I need it. And I need outside stimulation too - a job of some sort to keep my brain active.
I think the ideal situation for me would be to go ahead and have the third child, but to do it with some help from a nanny. I offered this idea up to N who was initially put off by the idea - and then very annoyingly brought up examples of women who stay home with their 3 kids without help. Fine! Let them! I'm not up to it though - that's not how I want things to turn out. It doesn't feel right for me. Mimi ain't rollin' that way . ..
Anyway, he eventually came around to accepting that we could use the help. In fact, the whole conversation turned out quite well because it resulted in us hiring a housecleaner. Just like that, viola! Love it! So excited! (this is another thing he was not crazy about initially ....).
Okay, so we're all on board for some help from a nanny . . .but I'm still a little apprehensive . . .it probably has something to do with going through pregnancy all over again. Arrrggh. Not my idea of a good time. The nausea, the tiredness, the aches and pains. And I'm not getting any younger over here . . .each pregnancy is probably a little harder as we age (right, tell that to that 60 year old who just had a baby!).
Anyway, I really want to get some feedback from those who have 3 kids and how they managed from 2 to 3 and what the change was like. I think I'll have to go out and get that feedback out in blog-o-land . . .