Keep your expectations realistic. So Cal APs definitely affect crowd levels. But don't be nervous and don't go into it with a negative outlook. A crowded day at
Disneyland can still be super awesome! I've been there during some really busy times and relatively slow times - of course less crowds are better, but I have still always been able to do almost everything I wanted to do.
First, I highly suggest you spend the extra money and do Max Pass. I cannot praise this system enough. We did everything, multiple times, with little to no wait. Second, if you can, get there at rope drop (or even better MM if you have it). Third, take afternoon breaks. Get away from the crowds and heat for a while and recharge your batteries and rest your legs. With Max Pass, you can book FPs from your hotel room during your break. So go back in the evening when the weather has cooled, armed with a couple more FPs.
If you have kids, have things to occupy them during lines. Wiki Stix are fun. Little snack bags are helpful. If it's just adults, waiting in line isn't terrible any way.
Also, make sure to have some kind of reservation for food, so you're not scrambling to find food when your hot and/or crowds are getting to you. That's a recipe for crankiness!
Definitely don't cancel your trip. Just go in with a plan and enjoy all there is to see and do
