@terribwyo The order of the day is patient first, car second. In an emergency situation, ALWAYS pull up to the ER doors, unload your patient and escort into the ER (there are nearly always wheelchairs by the door), get them to the triage/registration area, then go park your car. Usually you can ask, and there is a small dedicated ER parking area nearby, but not always. We have been in ER's all over the country and have never done any differently.
As to what to take, always bring his insurance cards and ID, any recent doctor's notes if you are outside his care network, and current list of all meds. Here is an excerpt from a recent post by @ocdogmom: "...Also, whenever I have to take him to a doctor's appointment, imaging center, emergency room, chemo appointment, I take my "go bag". This is a backpack that is filled with tissues (for his constant runny nose) his diabetic supplies, snacks for both of us, water, a book for me to read, a change of clothes and disposable underpants( he is incontinent) and anything else that I think would be helpful to either of us. For your sister it may be a small favorite object or some photos of loved ones that you may be able to distract her with while waiting..." I would add a sweater or hoodie for each of you, favorite snacks, water bottle for you (he should only have what ER gives him) and phone charger.
I hope he is doing okay now.