Will transforming Thing in the Ice with a token-summoning spell bounce my tokens?
You'll wind up with your Awoken Horror plus two zombies. Awoken Horror will not bounce your zombies, because the whole transformation/bouncing process will happen while Gisa's Bidding is still on the stack.

Here's the process, assuming players do nothing but keep passing priority after you cast Gisa's Bidding:


You cast Gisa's Bidding. It goes on the stack.
You have cast a sorcery spell. Thing in the Ice's triggered ability goes on top of the stack. (In case it's unclear, "when you cast" triggers happen right after you've cast the spell, before it resolves.)
Thing in the Ice's ability resolves: you remove an ice counter from it, and since it has none left, you transform it as instructed and turn it over to its back face.
Awoken Horror has transformed, and its triggered ability goes on top of the stack.
Awoken Horror's ability resolves, and bounces all non-Horrors.
Finally, Gisa's Bidding resolves and gives you two 2/2 zombies.