Things to look for in a jogging stroller...
Runner's World magazine ran a great article comparing baby joggers and came up with a top 15 list or something.
This is what they talked about:
Tire size. I think the wheels come in 12, 16 or 20 inches. If you are mostly running on the road you can do smaller wheels... the bigger ones are more fit for trail running or dirt roads. Bigger wheels also have a wider turning circumference so they are a little harder to maneuver but the ride is smoother.
Height... if you are tall you might want to try a few out at the store. Some of the handle heights are higher or lower than others and it may be uncomfortable when running. (mine is a little too low and I feel like it makes me have bad posture when I run).
Mine has a wrist tether so if I accidentally let go the stroller would still be attached to me.
Hand brake on the handle bar. Brakes on the rear wheels that you can set when you aren't moving.
padded seating, front wheel fender to keep mud from splashing up on your kids if you hit a puddle, bug netting, wind shield???
Weight and foldability. How heavy is the thing?? And is it easy to fold up and unfold? How small does it fold down?
Comfort... obviously for you and your kids. 5 pt. harness or not?
If you want to read the Runner's World article I think you can find it on their website. It was at least a year ago now.
Hope that helps.
Have fun running.
Oh... that reminds me... I always heard not to run with a baby who is any younger than 6 mos. They need to have really good head control before you start doing something like that.... They do have special "bassinet" joggers that are okay but I would be careful. I think 12 weeks is way to little.