To Give Up Mouse Clicks with a Cookie?

I have some long web pages. For example...

So during the past month I've added two buttons at the top right corner of all my web pages. One darkens the background for people who like that. One narrows the page to 800 pixels for people who find that more readable.

Currently a reader has to click the button(s) on every page they want the effect(s) applied.

I could change the buttons to "remember" a reader's preference, using a cookie. But I'm old enough to be prejudiced against cookies, especially needless ones.

Should I use a cookie, or should people have more anonymity and mouse clicks?