Cleaning the carbs means taking them off the saw, taking them apart, cleaning, then reinstalling with a rebuild kit. Probably could use new fuel lines, too. It's not too hard for me, but I don't know at what level you're working on your saws.
$100 for the lot is a good deal. The Poulan 306 is a a great medium saw from the late '60s. Also the best sounding ever made. Oh, and they used one in "The Texas Chainsaw Massacre." The Jonsey 70E is a larger saw from the '70s-early '80s. Very nice, sort of a little brother to my 111S. Probably worth around $150 restored and working.
I'd go for it.