We have a Senior pass in California! Can we use it? How many are allowed in the National park in that pass?

The National Lifetime pass is not good for state parks. You will need to fill out the California State Park Discount pass separately as this is a state park and not a national park.

The ranger accepted my military ID. I believe it's good for the car load.

Yes, and there is a Senior discount for entrance. Each entrance pass is one per vehicle.

there is a senior discount

Yes they do, they have a senior discount.