They'll like the mealworms fresh and wiggly please! No frying necessary!
Yes to grass clippings, but only in small amounts at first, and make sure they have some grit, I'm not sure battery hens get ANY grit due to their diets... so they'll need to get their systems adjusted to real food.
Don't forget to post pictures and save stories of how fun it is to see them becoming real chickens.
//edit// don't worry about dog wee. Not enough to worry about honestly. I suppose if you have an area the dogs love to go, you could avoid raking up that part... otherwise, please don't forget they're chickens, centuries old critters that are great survivors.