Well, this is a start. Chances are, you don't know the attending and the attending doesn't know you. You are taking direction from the resident who is directing the patient's care under the supervision of an attending physician who may (or may not) be the patient's "attending physician" of record.
The doctor may not see the patient "shortly". You aren't expediting anyone's treatment, you are there to learn how to take a history and physical.
Good luck finding the attending. He (or she) is 15 miles away in an outpatient clinic and won't make rounds until tomorrow morning.
I'm not a physician and I've never attended medical school so this isn't some esoteric knowledge that I have by virtue of being a doc...
I'd deflect some of the objection about my age by saying with a smile, "I guess I have a baby face."
Then I would go on with, " I would like to ask you some questions so that we, the team taking care of you, have as much information as possible about your medical history. We'll share this information with the doctors who will be guiding your care. I know that you've been over this with the doctors who took care of you in the emergency department and I hope you'll forgive me if I ask something you told someone earlier, we are trying to be thorough so that we don't overlook something that might help us figure out what's causing your problems and how we can help you to feel better."