My wife has a Heritage Redfish 12 that has a 2" crack in the seating area next to a scupper hole. What is the best way to repair that?

Your best option is Plastic welding

Other options that could work
Gflex two part hdpe epoxy
Fiberglass patch reinforced with 3M pl5200

How bad and what is the location? Scupper cracks can be tricky.

show us some pictures.. haven't seen a hole yet that enough JB Waterweld couldn't fix.

I had a crack around a scupper hole in one of my Reloads and I used some scrap plastic and wood burner to fix it right up.

G Flex epoxy works great but the surface must be pretreated by flaming with a torch.

In an area that flexes from weight and next to a scupper there might not be a good repair. True plastic welding is the best repair for cracks but is difficult and tool is some what expensive. Plastic melting with an iron of some sort are not that good and long term. Hard epoxies will crack off from the weight in the seat and flex of the hull. You might try some Lexel. It is better than silicone and stays flexible but won't stop a crack from spreading. Other than that we need some pictures to see where and how bad your crack is.

Don't know if I did this right but here's a picture