Probably not the perfect solution but its worked well enough for me if I understand the problem correctly. Instead of the IPO window, go to the NLA window. Here, box select all the keyframes that you want to slow down and put the green line where you want the interaction to begin (this is because blender scales away from the green line in the NLA window). Next, just scale the keyframes away from each other and tweak until the speed is about right. Finally, just tweak anything that ends up not looking right.
For the other model, this is simple. Just box select all relevent keyframes in the NLA window (much easier than in IPO window). Then just grab/move them to where the interaction begins.
save a copy beforheand though in case something goes wrong.
Hope that works and helps you.