Changing the bottom bracket is probably a good service item if it has play, creaks loudly, grinds, or otherwise shows signs of neglect or wear. Most modern BBs last for a few thousand miles under normal use. It's a cheap service item though, so it won't hurt to change it.
Why are you changing cranks? Unless yours are damaged, I'd keep them. The chain rings don't wear appreciably until you have many, many thousands of miles on them. If you do need the new cranks, go ahead and get the 122mm spindle; +/- 1 mm won't be noticeable either way.
I'd consider a new chain and cassette; these are wear items that wear out more quickly than front chainrings or bottom brackets.
Good luck!