Cook the cornmeal first (a cereal mash.) Your flakes have the starch gelatinized already, but the cornmeal will not. (If you get "instant" cornmeal/polenta/grits/whatever then it is also gelatinized.)
Alternately, save the cornmeal for dinner and augment your flakes with straight sugar. You will probably not notice the difference.
Fermenting in kegs is great. I
highly recommend a floating dip tube for future batches (and specifically,
this one.) Purging that pint or two is fine in theory but in practice that pint or two can gunk up your out post something fierce.