Was willst du heute machen?
Was möchtest du heute machen?
Was willst/möchtest du heute tun?
The first two are both fine, just the second being slightly more polite (möchtest - would like to, willst - want). The third one is not used. Both ',machen' and 'tun' mean to do, but they are not used in the same way. 'machen' is generally more used, like in common sentences like to do something. 'tun' is more used in special expressions like , es tut mir leid' (I am sorry), 'es tut weh' (it hurts, it is sore)etc.
(Google translate still doesn't work very well on sentences. Basically, longer the sentence is more likely it is to get it wrong)