I am a believer in prewashing my fabrics and then prewashing the quilt before sending. Other people don't do either but my household generates a lot of pet fur and dust
And, if something does go bad, I want it to be on my watch and if I can fix it or not.
So, if it really needs to go out right away, I'd include a note that you couldn't get it washed, plus general care instructions, and that if anything happens it wasn't something they did.
I've washed up to queen sized quilts in my home (extra large capacity) top load machine with an agitator. At some point in the last few years, I've gone to the laundromat for the larger tops -- for one because the dryer was so much faster. Warning, if you haven't been to the laundromat recently, a large capacity machine is not cheap!
In my new house I have an extra large impeller (no agitator) top loading machine and a nice dryer to go with it. I think it does a great job when I have to wash a lot of small bits of fabric or my regular clothing. When doing quilts, I make sure I make the water level deep, set an extra rinse, and typically 2 extra spins...