My LO wakes up screaming so I really don't get the idea that LOs will play in their crib for a while upon waking.
Do your LOs wake after the sun comes up? Are they playing in the dark? We have a nightlight in LO's room but it doesn't provide enough light for her to see toys.
After 10 months I'm trying to be done with the 4am wakeups (that have moved to 3am). I don't think getting LO to play in her crib is a solution but it's something that baffles me.