You could run all three with a SU-800 and the SB-400 would make a nice hair light. Unfortunately, you're limited with respect to what 3rd party triggers work with CLS. Most would be manual.
If you don't mind going manual, the Cactus V's are pretty inexpensive. You would need 4 of them at about $30 each. There are other triggers, but my experience is with the Cactus Vs and they work pretty well.
You'll want some modifiers such as umbrellas or softboxes, but with three speedlights should have a very flexible system.
"Red is gray and yellow white, but we decide which is right ....and which is an illusion"