Take AP CS A and do something with it. This will be more useful to you than to take two AP classes.
You cannot really take AP chem over the summer because 1° it requires labs and 2° it’s far too intense to be thus compressed.
What you can do is take two summer session classes at your local community college, one in CS and one in something else (I’d suggest Writing or Communication since it’ll show balance in skills + will be useful to improve writing skills, which you need for all subjects).