The purpose of raising the humidity @ lockdown is to prevent the chicks from dehydrating. You can leave a chick in the bator for 24 hours without feed or water because they're still living off the yolk but baking for 24 hours @ 100* with low humidity is the recipie for chick jerkey. 50% is kinda low in my opinion so as soon as they dry off and start moving around I'd remove them and get them started on feed & water.
Personally I try not to open the bator while eggs are pipping & zipping but you can crack the lid just enough to reach in and quickly snatch a chick without causing any drastic changes.