Dell PE R720 With Windows 2008 R2 Std - Serial Key Upgrade to Windows 2008 R2 Enterprise

We have several apps running on a Power Edge Server R720. We first started out unaware that this Windows 2008 R2 Std OS has a limited of memory up to 32Gb Ram although the physical server can support more memory than what we current have (96Gb on one CPU or 192Gb on dual CPUs). We just upgraded our memory to 48Gb from 32Gb and observed the installed RAM is 48Gb but only 32Gb available inside the OS of Windows 2008 R2 Std.

If we only re-apply the key for Windows 2008 R2 Enterprise so we can overcome the bottleneck of the Windows 2008 R2 Std. Do you think it will work on the fly with no issues on us after a rebooting? The server running MS SQL 2012 Std and a critical third party app for us.

Have you running into the similar situation like this and you have manipulated to solve? Can you please help with your advice?

Appreciated your time to help.