What should I include when accepting/rejecting abstracts for a special issue I'm editing?

Hi, I am currently working as a guest editor for the first time, preparing a special issue on disability for an interdisciplinary journal (albeit one that leans closer to the humanities side of things). I am at the stage where I have to accept and reject abstracts, but I'm not entirely sure what to include in my emails to those who submitted.

For those whose abstracts I am accepting, is it enough to simply let them know and thank them for their proposals? I'm also struggling a bit with how to address the rejections -- a lot of the work submitted is very promising, but there is unfortunately not enough space in the issue to include it.

Sorry if this seems quite basic! I am still very new to editing (and the reasons why the focus of the issue is what it is aren't necessarily helping that much).