I'd go with an iPad instead of the mini just to be on the safe side. I have a 12" tablet and it's night and day compared to my 6" Kindle (2020 model). Kindles suck if you try to read pdfs, they don't scale naturally so you can't see shit. Anything with a screen at 10" or more would work fine for pdfs.
i guess that would be an iPaid air as it just got refreshed?
Even 10" feels far too large to casually read in bed with.