Jeez CF, you sound like her mom.

I will respectfully disagree in a few regards. I don't think you need to make this overly complicated. Bells and lights are good things to have. A cell phone is not a bad idea either. However, you don't really need to wear tights, or any type of cycling specific clothing. You might find that type of clothing more comfortable on longer more strenuous rides, but for a few miles at a moderate pace, regular clothes are fine as long as it's not really hot or cold.

Whether or not you ride with a buddy is up to you. If you feel safe without one there is no need. There's also no need to methodically plan your trips. What fun is that? Same with letting people know about your route and estimated arrival times. If you feel safer doing those things then by all means, but I don't think it's really necessary. I don't know how much the fact that you have cerebral palsy impacts these decisions, but you're an adult and you can decide for yourself what you need to do for your own safety.

Riding with full panniers might take a slight adjustment but with the loads you're talking about I don't think it will be a big deal. It might be a little more unstable at really low speeds. It might be more prone to tip over if just supported by a kickstand.