more tempo changes

hi,  what i'm trying to do is record a song with a few tempo changes. my questions are, should I record the drums via ez drummer at one tempo then go back and change the tempo where I need it then record an audio track?? or, is it possible to record a audio track with a midi track (ezdrummer) then go back and change the tempos where I need them?? it seems when I try the latter that the audio track (guitar) goes out of sync with the drum track.
any idea, suggestions??
thanks