A lateral release, although an arthroscopic procedure, tends to have quite a bit of swelling and pain as compared to a meniscectomy or other simple knee scope. Doing one knee at a time will allow you to have at least one good side during your recovery.
Once you get through the surgery and rehab on one side, then you can have the other side done. It takes longer, but your recovery will be easier because you won't be quite so incapacitated.