If you know you will always have another adult with you, I
suggest a double and a single.  Most triplet strollers are
big and will limit where you can go.  If you know you will
have to take the kids out on your own, get a triplet
stroller.  I have the Peg Perego triplet stroller, the Baby
Jogger triplet jogger, and the Choo Choo wagon.

The Peg Perego is great for doctor's offices, and malls, and
places where the sidewalks are narrower.  I prefer the jogger
for walking around.  The choo choo had to wait until they were
older, and now that they are three, they are getting to be a
little too heavy for that choo choo.

Also, make sure your car can fit the stroller.  The Peg is a
little challenging to fit into most cars while most joggers
can fit many cars.