I have had some success with a homebrew range finder that costs about $10(US) to produce.
It uses a cheap red laser pointer, photodarlington, filter, and spinning mirror. I usually include a dedicated PIC micro to turn the timing into serial range data for a master micro.
Range is good from 3" out to 50’ depending on conditions. And accuaracy is traded for refresh rate depending on how fast the mirror spins - since it uses the triangulation method. Range resolution of <1cm updated @40KHz is what I often use.
The problem I can see using this for your application is that a car could crash into a chair leg because the laser range finder might be pointed to one side or the other. In this case the more coarse resolution of sonar sensors may be a benefit - I have had good results from MAXbotics EZ1.