Yep, snakes appear to be very robust when it comes to the effects of inbreeding, showing no sign of issues for generations.
Most people play it safe by only inbreeding for a couple of generations before they outcross again.
I'm impatient, so I'd probably hold back all the females, and one male. I'd breed the male double het back to the mom, and keep back all the visuals.
I'd prove the visual males on a female of the other morph (if you have one), if possible.
I'd pair them with the double-hets when the double-het females are of age, to increase my odds. If a snow isn't produced, I should have at least confirmed which of the visuals are carrying the right gene, which increases the odds for the next year.
It doesn't increase the over-all odds of snows the FIRST year, but it increases the odds per egg in clutches where your visual males DO carry the other gene. Once you have them identified, your odds will be better the next year, too.