My kids were 16, 18 and 20 months apart and knowing what I know now, I wouldn't have changed a thing. With the exception of my oldest who is isolated from her sisters, the younger three have had each other from the word jump. There was a time when they all had each other and who knows, maybe will again.
Having small children close in age is no cake-walk (having needto and angel's little ones here for a week reminded me how hard it was LOL) but I do firmly believe that the pros outweigh the cons. You have to teach them to get along from a very early age. Yes, it won't always be paradise but I do remember that once I got rid of my ex my girls and I were JUST FINE....
I am thinkin one of the benefits of not having another parent in the house is that you won't have anyone undermining all the good stuff you are instilling in the kids.
Either way, I hope it works out for you and you get the family that you have always dreamed of. Not a lot of conventional families left out there but that doesn't mean that your family will be any less happy.