This Max for Live technique will let you adjust the BPM of your full set in Ableton Live Session View.
You can play things a few (or more) BPM values faster and slower and all pre saved BPM values will be adjusted, so your pre-set tempo feeling of your Scenes in Session View will follow the adjustment you made automatically.

Also check out the two used cases in the videos below. Learn more on adjusting Ableton’s Session BPM and copying tempo info from one set to another.