I'm not so worried about the birth, although I'm not sure I want it completely natual this time round, I had a seperated pelvis at 36weeks which was so painful and I had to wear a belt just to keep it together! And I was in the latent faze of labour for a week and only dialated 1cm! then when I was giving birth the cord got wraped around her neck which really freaked me out. I think though part of the problem was having an inexperienced midwife who just took the "wait and see approach" instead of hurrying my labour along.
I don't think your crazy for trying for #4, if everything goes smoothly this time round then we will be doing exactly the same thing.

But you must be superwoman to have them so close together!