First we went with Angelina Ballerina by Katharine Holabird, a book I remembered loving growing up. I actually wound up buying a 25th Anniversary edition, and since I'm also 25 it seems to make perfect sense that they would a part of my childhood. I was actually a little surprise to see the listing in the back of the book as to how many Angelina books there are now. If I remember there were almost 20 or so! I only remember owning 1 or 2 myself.
The second book we decided on was Julius Baby of the World by Kevin Henkes. This is actually a book I don't remember ever reading or owning. However I do remember having a few Kevin Henkes books that I really enjoyed, so given the them of the book I thought it was a perfect fit. In case you haven't guessed from the title, the books about an older sister who doesn't understand what's so great about her younger brother. That is until someone else decides they don't like her brother either, and she feels the need to stand up for him. Since she has a younger brother about 2 years younger, and there's normal sibling jealousy issues I thought it'd be almost perfect.
Overall it was a lot of fun, and while I might not be ready to have my own children right now, its still a good time being around other people's babies.