Personally I would space getting them apart instead of the same time...to ensure puppy bonds with you....
I have three. Added one when the first was a year old, then another when the second was a year old.
It certainly helped with potty training...then again...I've been potty training a new puppy...for three years now. Maybe I wasn't as smart as I thought.
ETA: Also just note..if you get two at the same time...your first year vet expenses will be doubled instead of spread out.