Source accuracy with different web donation options

Hi all! I'm hoping someone can offer a suggestion for a question I have.

At my organization, I run our calendar year end and fiscal year end annual fund campaigns, and during a campaign, we use several different donation asks that would take someone through the website (eg: email, QR code on a slide show, QR code on the brochure, clicking in from the website itself, etc). I would like for our sources to be as accurate as possible, so that I can better understand the impact that each has and know if I need to revise or keep something the same, and so I'm wondering if there is a way to know how someone donated (whether they clicked in from an email or scanned a QR code).

For our last campaign, when I asked him about it, the person who manages the website (who is also a long time Tess user) made me different donation pages with unique links that each had a specific drop-down pre-selected, so that it would say something like "A gift to the Annual Fund (email)". I then took those links and applied them in the appropriate places. Unfortunately, they never quite worked as we had hoped, as when my colleague who handles gift entry was entering the donations, she could only ever see that they were gifts to the Annual Fund, but didn't see the rest of the text on the drop down line. 

Does anyone have anything that they've done that would work in a situation like this? If it's relevant, we haven't yet upgraded to v16, and this is what our donation page looks like (I don't know why graphics aren't loaded, it's normally prettier.)

Thanks in advance!

-Sydney

Sydney Wilkins
San Diego Symphony
Annual Fund Manager