Looks ok. As long as it has a ceramic element it should be ok. As you've got separate fans anyway to circulate the air, would you consider oil-filled convectors safer than fan heaters?
:-)
I've been using ordinary (metal filament) fan heaters for years in greenhouses. Never seen one fail dangerously. Even when the fan didn't work and the element overheated, the thermal cut-out worked to disconnect the supply from the element. But then there's not a lot that can catch fire in a greenhouse...