What doesn’t make sense is your use of the term “offline editor” - it’s entirely nonsensical in this context. If they can’t use an offline editor, they won’t be any better with an online editor. It’s like saying you need a 4 door car because you can’t drive a 2 door car - it’s the same thing with more seats. Photo editing is photo editing regardless of where the software is hosted.
Just use imgflip.com - that’s all it does is add text to images.