I just wanted to add this. Not all dog crates are created equal. Meaning,, the distance between grate wires/rods, can vary. The larger crates tend to have wider spacing of the wires/rods. ( I know, having multiple size crates)
My suggestion, so your chicks do not escape, or get stuck trying;;

;;;; fashion a cardboard strip around the bottom perimeter of cage. 8 inch high should be enough. Chicks will not try to fly up, and thru the wire opening,,, but they may try to walk thru on the bottom.
Another suggestion,, is placement of brooder. If you can place on top of table, or similar, then when you approach the chicks, you are from the horizontal direction. That makes chicks less stressed, and scared of you. By natural instinct, , chicks fear anything that comes from above.