If I want to make the cookies chewy as opposed to crispy, what would you suggest?

From CI: If you want chewy cookies, add melted butter. Butter is 20 percent water. Melting helps water in butter mix with flour to form gluten.

I like chewy too; for all the sugars I would use all DARK brown sugar and no white sugar (the cookies will be darker, or follow the karo syrup idea mentioned) and replace 1/2 cup of the butter (1 stick) with 1/3 cup veg oil. An extra egg white sounds good too.

Use a lower protein softer flour. Either white lilly, or Martha White...if southern blend of soft AP flour isn't available..use 1/2 USDA AP flour and 1/2 cake flour. And as mentioned under cook them a bit and use karo syrup. Don't over mix the cookie dough as it makes tougher protein strands.

And I'll admit I haven't tried but maybe a 1/2 tsp of unflavored gelatine bloomed in the milk mixture would hold moisture without throwing the recipe off--as some recipes for chewy oatmeal cookies call for jello mix in the dough. (which never appealed to me...strawberry oat meal cookie; I'll pass).
Or maybe take out of couple of tablespoons of milk and add egg whites.

Another way is to replace a bit of the brown sugar with some Karo syrup, perhaps 1 or tablespoons of the former for the same of the latter.

The easiest way is to slightly undercook them. If that doesn't work, add a slight bit more brown sugar.