Great, really. Stan was good, and the parents were also pretty well. I specialy liked how you concluded the naming part, leaving they to call him Dipper until they come up with a real name.
I think his name will rhyme, don't you think? Another possibility is that Dipper is his real name...
Hey, I wrote some fic with this same scene inside it, you probablly would like it, so why don't you check it out... come on, I know you wan to.

I love it :D, you could keep writing this fanfic?

Only one problem: Dipper and Mabel were born five minutes apart.
Other than that, the fanfiction was great and I enjoyed it.