My comment edit window closed, but if you trust me, I also made up a quick little pre-baked shortcut that should be fairly user-friendly[1]. Will prompt for date range input, calculate and display total upload size, ask for confirmation, prompt for upload location, then show an alert on completion. Also has some very rudimentary error handling in that it takes a file count before and after the upload, and warns if the two counts don't match up.

A few things to note (applies to my above comment as well):

-If you have a less powerful iOS device, your screen may go semi-unresponsive during the upload process. My iPhone XS goes unresponsive until the upload finishes (less the ability to terminate the shortcut via the "stop" button), but my 2017 iPad Pro is totally usable during upload.

-You may get an error along the lines of "This Shortcut is trying to share more than [x] photos." You can allow this by going to iOS Settings > Shortcuts > Advanced, then toggling on "Allow Sharing Large Amounts of Data"

-Again, there's no progress bar, so it may help to run the Shortcut from the editing pane in the Shortcuts app. That way you can at least watch the app step through the script.

[1] https://www.icloud.com/shortcuts/d3258e1d720548cd9e635bbe090...