Chick starter, grower or an all flock type feed would be fine to feed the entire flock. Given the age of the chicks, starter would be optimal for a few more weeks, for the extra protein, but each brand of feed is different so you want to check the nutrition panel - some growers/all flocks have as much protein as some chick feeds.
A few bites of layer won't harm the chicks. But the more calcium they take in, over a prolonged period of time, the greater possibility of kidney/liver(?) issues once they're older, as their bodies aren't meant to process the extra calcium a laying hen would ta