Baby Jogger and BeBe Love both have tripple joggers, but they are side by side. Overstock has some right now: http://www.overstock.com/Baby/BeBeLove-Aqua-Triple-Jogging-Stroller/5174231/product.html?rcmndsrc=2
There is one that is a tandem that will hold 3 (or 4) http://www.stroller-advisor.com/runabout-triple-stroller.html I know of a couple of people who have them and like them.
There is the valco twin tri mode w/ toddler seat, as previously posted, but I would not use it as a jogger. It does get harder to push when you have a big kid (~35lb-40 lb-- the limit on the toddler seat is 40lb) but that stroller is a dream and I LOVE it.
We are extremely active too. I had 4 kids in 3 years. I have the valco w/ toddler seat and use it almost every day. It is super easy to push and steer. When the babies were little I'd try to shop alone, late at night, or I'd wear one, put one in the stroller, a toddler in the toddler seat, recline the other seat of the Valco and put my groceries in there. THen my oldest (who was almost 4 at the time) would either stand on the jump board on the back of the stroller (which you purchase separately) or he'd walk next to me and "help". That really only worked for small shoping trips-- for big, monthly ones, I'd either take someone with me to push the stroller as I pushed the cart, or I'd go alone :)
As they have gotten older I normally put one in the cart (in the seat part) and wear one on my back or chest and then the older 2 are old enough now to walk with me.
The nice thing about the valco w/ toddler seat is there is a lot of room and storage. And if your toddler wants to walk, you can still add the toddler seat and put the diaper bag or wahtever in it, that way you can have your hands free. I would buy that stroller again in a heartbeat, I love it. And I am EXTREMELY picky about them.
Now, all that being said, we are very physically active-- biking, running, walking, hiking, etc... so in addition to our valco I ended up getting a Chariot CX2 and a Chariot Cougar 2. We can take all 4 kids bike riding as a family and run/ hike together too. When it is just me w/ all 4 kids and we want to do something like go to the park (which is too close to justify driving to, but too far for the big kids to walk to) or walk around the neighborhood, I'll pull one stroller w/ the hiking kit and push the other. It looks a little crazy, but it works really well.
Congrats on your babies! I can't even imagine that surprise! I had 7 months to get used to the idea and 2 years later I'm *still* trying to get over the shock :)
Let me know if you have any questions about the strollers, I'm good at strollers, not so good at baby wearing 2 babies.