If doing it via the CLI is the same as using the GUI program, then it should work fine. It will do an online expansion, so you won't have to take the system down while that's happening.
The first step is adding the 2 new drives to the array, and then you can expand the logical volume using the new space.
Once that's done, you still need to use whatever process on the operating system (I don't know much about ESX) to expand the partition to use the new space, so you might want to check the documentation on that if you're not familiar with it. I just know that with Windows it's as easy as selecting the partition and expanding into the extra space available.
The first step is adding the 2 new drives to the array, and then you can expand the logical volume using the new space.
Once that's done, you still need to use whatever process on the operating system (I don't know much about ESX) to expand the partition to use the new space, so you might want to check the documentation on that if you're not familiar with it. I just know that with Windows it's as easy as selecting the partition and expanding into the extra space available.