I think the greige sounds good but as to specific color the best thing to do is to grab a bunch of paint swatches and look at them in the actual room. With colors like that the daylighting and nightlighting the room gets are really going to affect the choice.

I think you will get more mileage out of your greige choice as a neutral backdrop than you would a typical "girl color" . If at 4-1/2 she suddenly hates pink, you could easily shift gears without repainting.

I have the same bedding (sheets) from Land of Nod. I paired it with BM Nimbus in my daughter's room. It's leans more gray than beige, but it goes well with the bedding.