How do I communicate my friends-with-benefits rules in a kind way that won't upset the other person?

I have a few rules for friends-with-benefits relationships to help maintain boundaries and to avoid any unnecessary confusion, expectations, or emotions. Honestly, I rarely have to mention or enforce them.

I have a new FWB and we have only gotten together once, a few months ago. FWB is young (I am officially robbing the cradle) and very sweet… and really wants a sleepover. The first time, I was able to avoid hurting feelings because of my living situation. This next time, my roommate will be gone and the topic of a sleepover has come up again.

I like to snuggle and all of that, but I very often don’t want a sleepover because I don’t want there to be any emotional confusion, but also because, frankly, I don’t want to have to deal with awkward mornings-after where I try to politely extricate myself/them from each other’s company. I know that might sound heartless and I assure you that I am not; it’s simply the truth.

So, how do I nicely communicate that I don’t want a sleepover without hurting an extremely nice and sweet person?