I would go with easily digestible things stuff you would offer a duckling. Scrambled eggs, maybe mix some flock raiser with a smaller amount of grower feed you could make it with liquid electrolyte water and let them play like it is nutrition in a puddle. I would also keep all needs close to each other. every thing in an 8x10 area should allow them to feed forage and exercise without overdoing it.
Good luck, glad they are in their loving home again.
Bless BYC and all their smart ppl willing to share info, hope, faith and prayers