I'm just going to provide a rough guide instead of total details, because there might be a problem either way.
You could create four new empty databases. Into each of those databases, drag and drop one of your grandparents, plus all their ancestors and all the descendants of those ancestors. You don't have to mark each person to include in the drag and and drop, one at a time. You can do a bulk marking, and I'll leave the details as an exercise for the student.
But the problem you might run into is that your lines might cross. If they do, there is a possibility that a lot of the same people will be dragged and dropped to more than one of your four new databases, and that one or more of them may end up with more than your limit of 10,000 people. For sure, you yourself and your own family will end up in all four databases, but that's a pretty minor issue in the grand scheme of things.
You obviously know more about your database than I do, so you may have a pretty good idea already how likely you are to have crossovers between the lines of your for grandparents.