You can bring your own petals if they are
real, and you will not be charged for cleaning them up.
I considered ordering a bunch from
www.flyboynaturals.com - they seemed to have good sales, and they also sell bags/cones/etc.
However, when you bring your own, you have to put them into containers (or a big basket) yourself and then designate someone in your party to pass them out - Disney won't do it for you. I figured the not-huge cost savings weren't worth the hassle, so I just bought toss petals and aisle petals from Disney.