How old is your son? Both my husband and I are training for a half marathon in a few weeks, we have 2 kids under 4 years-old, and trying to run with them has been a nightmare. So, we've had to get creative with alternating our runs.
Hopefully, your son will be much more conducive and less needy than our kids who bore easily (son is almost 4, daughter is recently 2).
We have a BabyTrend. It's OK - I don't like the stationary front wheel. But, I'd recommend finding a store that caters to serious runners (locally we have the Running Company - erunningcompany.com for point of reference), and they carry jogging strollers for serious runners. Most double strollers we looked at would be at least $400 - I believe it is a BOB.
Good luck.