The LK-280 has a USB port for computer and MIDI connections, so you'll need a standard USB cable (sometimes referred to as a "USB printer cable") to connect to the iPad. However, since the iPad doesn't have a USB port, you'll need to use an adapter that lets you plug a USB cable into the iPad. This is usually accomplished by buying an iPad Camera Connection Kit, which actually contains two adapters-- one for using a USB cable to connect a camera or other device (including a musical keyboard that has a USB-MIDI port), and another one for reading and writing to an SD card. Since the LK-280 has an SD slot, the Camera Connection Kit would be killing two birds with one stone, since you could use the SD card adapter for copying files between the iPad and an SD card, then plug the SD card into the LK-280 for copying files between the SD card and the LK-280.
Note that the model of iPad could be an issue, particularly if you have a recent model-- at least, I've seen posts here and there from people who had trouble getting the Camera Connection Kit to work with their iPads and instruments. I don't know what the problem was, but if you've got a newer iPad, you might want to visit an iPad forum to see what's needed to connect your specific model of iPad to a USB device, such as a Lightning-to-USB cable.
You shouldn't need a USB-MIDI driver for your keyboard, because the iPad should handle that. But I don't think you'll be able to transfer files between your LK-280 and your iPad, because the User's Guide indicates that you must use the Data Manager software to do that, and Casio doesn't seem to have a version for the iPad-- as far as I can tell, it's strictly a Windows program.
However, if you want to copy files from your iPad to your LK-280, or vice versa, you can put the files on an SD card to accomplish that.
Otherwise, if you want to play your LK-280 and record its MIDI messages on your iPad, or use your LK-280 as a MIDI keyboard controller with iPad apps, or use iPad apps to send MIDI messages to your LK-280, you can do that over the USB connection.
On the other hand, if you want to record your LK-280's audio output with your iPad, you can use your iPad's built-in microphone to capture the sound from your LK-280's built-in speakers, or better yet get an audio interface. I have no experience at all with audio interfaces for the iPad, but the Griffin StudioConnect has audio and MIDI connections and is affordably-priced-- although it may or may not work as well with newer iPads (I can't tell for sure from the customer reviews), and the reviews seem to be a bit mixed.
As far as DAWs, note that GarageBand doesn't let you save MIDI files or stream MIDI data to a keyboard, so you'll probably want to read up on the latest reviews for the DAWs that are available for the iPad and buy one that does everything you need.
