Synthrapol is designed to suspend unset dye particles in water so they are washed away. This is what you would want to use on this quilt, as it will work on lifting up the bleeds (which probably have not been chemically set or heat set at this point). It can take several washings with Synthrapol to remove all traces of a bleed, so be patient.
You definitely do not want to use Retayne on a quilt. Retayne would permanently fix any unwanted bleeds, making them impossible to remove. Retayne is wonderful for yardage, before it is ever cut and sewed into a quilt, because it will prevent the type of problem your mother had when she washed the quilt for the first time.
Be sure to use a washing machine that has plenty of water in it. A home front-loader, for example, will not supply enough water. You want enough water to make sure that dye particles lifted out by the Synthrapol are not too concentrated in the wash water; you want those particles dispersed as much as possible. It wouldn't hurt to throw dye catchers in with the Synthrapol too.
I don't know about the ice treatment. Might be worth a try on one spot to see what happens. I can't imagine ice would set a bleed.