I wish I could give you the magic words that would convince the skeptics but I just don't think they exist. I know many people that have bought a car right off the lot, new, and NEVER question how well it was made or who made it. Yeah, gravity isn't a factor with cars and yes there is a warranty but YOU will know how well built your plane is.
My wife was on board from the beginning. She likes to fly, she even likes to fly with me
IMHO, as long as you live under your parents roof you should respect their wishes.