It's safest to ask your collaborators what they would prefer. You can't include them as coauthors of an extended abstract without their permission, and they might be upset if you leave them off. (Even if doing so is standard at this workshop, they might not know that or might disapprove of this standard.) I'd guess that they would politely decline authorship of the dissertation abstract if asked, but there's no way to be sure other than asking.
But first I'd recommend asking your advisor about this issue. I'm not sure what sort of workshop you mean, which suggests that this may be field-specific. In that case, you need to be aware of the conventions of your field and this workshop in particular. Presumably you aren't the first person to submit a dissertation abstract to this workshop, so this issue must have been dealt with before. If your advisor doesn't know offhand, then it's worth looking through past years to try to find examples. (As a last resort you could ask the workshop organizers for advice, but you shouldn't bother them with this unless you have to, and I'd be very surprised if you had to.)
Then you can write to your other coauthors and say "I'd like to submit an extended abstract of my dissertation to Workshop X. When people have done that in the past, coauthorship of papers appearing in the dissertation has been handled like this: ... Is it OK with you if we do the same here?" It's worth including a copy of your proposed submission, so they can see exactly how they would be mentioned if they won't be authors.
If you don't include them as formal authors of the abstract, then of course you should make it very clear that this is merely a summary of work published elsewhere and who the authors of those papers are.
