Playing devil's advocate here...
First off, let me just say that I've never actually watched this movie. I remember when it was released and all the negative criticism surrounding it. Therefore, I (probably rightly) decided to give it a pass.
Recently, I watched the Nostalgia Critic's review of it and I decided to come here to check out some other opinions. Two main criticisms seem to be prevalent.
WARNING: SPOILERS AHEAD
1) The "offensive" racial and ethnic stereotyping of the prospective parents.
2) The "cop out" ending where it all ends up being a dream.
Now, if this all was indeed just an 11 year old boy's dream, then wouldn't that mean the entire film was told from his perspective? Therefore, wouldn't all the characters act as he would imagine them to act? An 11 year old boy from a predominantly white upper-middle class suburban community probably wouldn't know all that much about different cultures. He would most likely only know these cultures by how they've been portrayed in the media, and what little he's actually been taught in school about them (which probably wouldn't be much). Therefore, isn't it likely that he would have a very stereotypical view of them? This would not be due to bigotry or to be purposefully insulting or offensive, but simply out of ignorance and lack of worldly experience.
Also, seeing as the film is told from his fantasy/dream perspective, wouldn't it actually be disingenuous and unrealistic to have anything but a stereotypical view of these different cultures? In fact, wouldn't the comedy/charm come precisely from seeing just how far removed from reality his opinions/expectations are regarding these cultures? After all, it's not like he intends to be malicious in his thoughts. He simply doesn't know any better. As for the dream ending, that's the only way this could actually work. To be anything but a fantasy/dream truly would be offensive.
Lastly, I've also seen the film criticized for its use of profanity/adult themes. However, from what I've seen mentioned, these aren't anything that would be atypical of an 11 year old boy...especially considering that in his dreams he wouldn't necessarily be on his best behavior.
Again, I've not seen the film so this is not an argument as to whether it is good or bad. It's just something that crossed my mind as I read through the pages upon pages of negative reviews for this film.