Given that this is, in fact, a nickname, which doesn't require a trip to the courthouse to change, I'm not too stressed about it. If the boy's father and I choose to spell it different ways, it will probably confuse people, but c'est la vie. I figure he's likely to switch over to his first name (which is also Pedro's Real Name, hence the middle-name appelation) eventually, because it's a beautiful, beautiful name, but I'm really trying my best to avoid having people call him "Junior."
We are, however, encouraging friends and family to bypass the given names altogether and stick with nicknames like "Hawkeye," "Deuce," and "The Sequel." "Version 2.0" is also acceptable.
Mostly, I like "Pearce" over "Pierce" because it's internally consistent. That, and if you get halfway through writing the nickname and realize you're supposed to be writing his full name, like on a medical form or something, you can finish it out as his complete middle name and cram his first name in front of it without crossing anything out. And also I don't want to encourage him to put holes in his body when he reaches the age of fifteen and decides he needs to rebel by dyeing his hair pink and wearing his underwear on the outside, or whatever the style happens to be in 2020.
All things considered, I think it's high time this thread were split and a poll added.