In this scenario its personal preference regarding which updates you perform first.
TBH, I would work out and document my update process for SnapDrive and SnapManager first and complete this work first.
I'm presuming your Exchange and SQL environment is all VM's and the environment is quite important.
Once the upgrades are complete, i would allow the enviroment to settle/bed in for a few weeks and make sure there are no underlying issues or niggles.
You will be able to run the same VM's with the same OS, just updated versions of SnapDrive and SnapManager for Exchange/SQL on older version of ESX
After that, I would start planning to update the ESX environment either via update manager, or possibly by reinstalling a new version of ESX and adding the old config back in.
Hope this helps.