I don’t think skipping AP Calc is a good idea for a future CS major when it’s available at your HS. AP Stats is generally considered a lighter weight AP. My son still found it very useful and was able to take it the same year he took AP Calc AB. How bad was the struggle in Pre-Calc? Any difficulties in Pre-Calc should be ironed out now IMO or they could muck him up in Calc. My suggestion would be to buy another textbook or practice problem set with the solutions or get an on-line tutor if that is affordable.