We get a lot of questions about tube and tyre size names because they're confusing.
In your case the tyre and therefore the wheel are both a ISO or ETRTO size of 559mm across, and the tyre has a width of 54mm, or around 2 inches. Your rim suggests that the tyre should be 1.5 to 1.75 inches in width.
Therefore someone has put a slightly wider tyre on in the past. As long as its not rubbing on the frame or the brakes, you're okay with a 2 inch tyre.
Since you have a 2 inch/54mm tyre, your tubes should be sized for that dimension. So you need a tube that covers the 54mm width of a 559mm tyre (aka a common 26" tyre)
Since you already have a 1.75" tube, it would probably work fine. Butyl rubber stretches nicely, and the only downside is a slightly elevated risk of puncturing, while being a little lighter.
Your third option is to simply patch the existing inner tubes and refit them, presuming they've got holes and no longer hold air. Not a big deal, and cheaper than new tubes every time you get a flat.