I checked this out late last year as a relative going overseas had much the same question. The relevant ipad user manual said that the only way to xfer data was via iTunes (it might even have been to the cloud) or most certainly via a wireless enabled external hard drive.
I am sure that others with an ipad will be better placed than I to comment, but the xfer regime does seem to be really restrictive.
The iPad connects to a Windows PC much like a camera. Use the Lightning to USB cable to connect it to your PC. Allow access on the iPad. You'll be presented with a DCIM folder where video and still files are kept. Copy them to you computer.
Or the client could do the same thing and bring you the files.
I have an iPad Air 2 along with my primary computing platform Windows 7 64 bit.
The way you transfer video, photos, etc. is via USB using the Apple Lightning Link USB cable, and iTunes for Windows running on your PC. Any other method will be taking the long way around to a simple solution.
"...it sounds like I'll need to install iTunes first."
If the media files are in the DCIM folder presented when you connect the iPad to the PC via USB then you can drag and drop the files from the iPad to the Surface. iTunes may make it easier for humans to do it but I backed up an iPhone and two iPads this weekend and I haven't had iTunes on a machine of mine since I threw away my iPod Shuffle. I'm frequently accused of missing the point and perhaps I've missed the point of iTunes here.
Just to reinforce what John Dennis posted, there is NO need to install iTunes. Just connect your iPad to your PC. Under Win 7 go to the Start button, select Computer, scroll down and you will see your iPad under Portable Devices. Right-click and an option appears to Import Photos and Videos. Click on that option and you're done. Again, no need to install iTunes.
My probllem has always been getting video from other programs (e.g. HT Recorder +) which don't store their files in the DCIM folder area w/o installing iTunes (which I'd rather not install). Moving those files on the iPad seems to be impossible.
When connecting the iPad to the PC I do get the DCIM and subfolders, but the HT Recorder files (and other 3rd-party captures) are not there. I believe they are in the ~/Documents area, but have not been able to access that yet via USB.