Usually for food size, you want to go with something no larger than the space between the frog's eyes. The exception to this would be nightcrawlers, since they are so long. A big part of the reason for this is that impaction (severe constipation) is one of the most common problems for these frogs. It can be caused by anything from feeding prey with hard to digest body parts (like mealworms) to feeding food with too high fat content (feeding too many pinkies; the rule is about one pinkie per month).
I personally wouldn't recommend the chicks. They have some pretty hard to digest body parts, and they're expensive compared to safer foods like nightcrawlers and pinkies. It probably can be done, but IMO it's not worth the risk. There's no nutritional benefit in a chick that they can't get from other safer foods