Good advice and tutorial on POE and managed switch choices.  The recommended GWN7711 is a great choice since you already have Grandstream router and access points.  

The no-charge GWN Management, local or cloud, available for these devices is useful for the novice or expert.  I have used the cloud solution for years to assist a relative, on the other side of the world,  monitor and update their network.  The Grandstream equipment has been reliable and stable.