ALL apples are edible, from the tiny crab apples to the big ones. The thing is, some apples get mushy when they are cooked and some do not. Since you do not know the variety, the way to find out is to use some in cooking and find out.
I m Diabetic, and I have a very simple cooked apple recipe. Basically, I cut up an apple peel and all, and I microwave it. I then put about a tablespoon of liquid coffee creamer on it, and I eat it. I think it is very good, and that would tell you how the apples would taste when made into a pie.
I think I should now go and cook an apple for tonight's dessert: it has been too long since I made some! YUM!
(In the interests of fairness I should say that few diabetic desserts taste quite as good as the ones with sugar in them, but I do enjoy my cooked apples)