Your parents would be entitled to bring in a guest to the lounge.
If the red cap will get you to the train the car attendant will usually be right outside the car and you could speak with him/her there. Ask nicely and you usually will get accommodated. If the train is going somewhere were you can buy a cheap ticket. You could cancel ticket before train leaves.
For example Chicago to Glenview on Amtrak Empire Builder is only $9.50. If you get off the train and cancel before train departs you will get a credit of $9.50 for future travel but if you want a refund you cancel and there is a 10% or $5.00 minimum fee.