Ok, gotcha. If you don’t care about georeferencing then you might look at EasyZoom. Since you will be flying so high I really can’t quantify the end file size and what cm/px you will be able to download, but I just tried 150 acres at 8in/px and the file was only 12MB. Yours was about 3500 acres, but another map of 200 acres at 2in/px was 178MB which is 4x the size or approximately 800 acres at the lower resolution.
Another option I came across was sharing directly from a Google Photos account to a website via HTML. May be worth a try.
The only other thing I can think of that might be an issue is the pixel count. Many programs have issues once one of the dimensions reaches 50,000 on X or Y.