Not sure how valet parking has to do with driving someone to the doctor. But I tip the valet attendant 2-8 dollars; depending on the location & event.
If you are driving a senior to the doctor and you are embarrassed when she gives you money you can always say no thank you to the tip. Most seniors are on a very tight budget but are also very appreciative to those who help them out.
Please don't ask her for more money that's just mean. I think it's sweet she gives you a dollar tip. She probably thinks that's a lot of money. Remember when she was a teenager that was a lot of money!
Why are you taking ANYTHING from the elderly? Kinda small of you. Anyhow your not providing valet servuce. Its more a taxi or shuttle service. Expecting old folks on probably fixed incomes to tip anything at all, let alone not being happy with the dollar they do give, casts you in a pretty bad and selfish light. Yoyre either already getting paid or youre a volunteer. Either way you shouldnt EXPECT a tip, certainly not a specifuc amount. I refuse to tip anyone who acts like they deserve it. When i tip its for good service and that includes a polite, unentitled attitude. Expecting more than a dollar from old folks! Esp when that dollar may be more than they can affird! Shame!