We used a Burley Solo trailer and a small reclining car seat that we strapped securely to the base frame of the trailer. It could equally well have faced backwards, but since the seat reclines so much that he was practically lying down I doubt it would have made much difference. The car seat took so much space that a regular size seat wouldn't fit, though, so when he outgrew the small one we put him straight into the built-in trailer seat. Which was pretty hammocky and gave poor support, to tell you the truth, especially with a bike helmet stuck on top... I think I would just count on keeping to a safe speed.
One thing that we never bought but I really wish we had was the add-on single wheel thingy for older kids, where they can pedal for themselves or just sit and enjoy the ride. I think it would have been a blast to have!
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett