Dont use retayne - you dont want to set the redcolor where it does not belong.
For tie dye, (fiber reactive dyes) the instructions are to rinse starting with cold water, ending up with hot water, and i beleive synthrapol in the final hot water. You could call the fabric manufacturer for advice.
However, you need to figure out what kind of dye is on the fabric - is it fiber reactive or something else? This website has a detailed technical explanation ... And paula burch knows her stuff!
http://www.pburch.net/dyeing/FAQ/synthrapol.shtml
After reading the above, i would suggest making a mini sample of your quilts whites and reds, and testing the synthrapol + very hot water wash.