Skylight only needs Wi-Fi to get set up the first time and download photos to the frame. All other features will work without Wi-Fi.
You can set up the frame for your loved one by connecting it to a Wi-Fi hotspot (using your phone or another tablet that has hotspot access). When the frame is not connected to Wi-Fi, any photos you send will be stored in your server. When you visit, just connect your frame to the hotspot again, and all the photos you've sent will get downloaded!