Yup, they'll work - tubes should work* with any lens, even a reversed one for extreme macro.
But the magnification is relative to the focal length - so adding 50mm of extension tubes to 200mm doesn't get you super close, show stopping macro shots. Using it at the 70mm end will produce higher magnification shots (although probably not 1:1), but less working distance.
Also, check out How can I estimate the reproduction ratio of an unknown macro setup?How can I estimate the reproduction ratio of an unknown macro setup? and How can I calculate the change an extension tube makes to the maximum magnification of a lens?How can I calculate the change an extension tube makes to the maximum magnification of a lens?
*Obviously if they don't have electrical contacts you'll lose a lot of auto stuff, but that's not relevant to the focal length issue.