She will be happy to sit on them. I usually switch my eggs by taking the momma off the nest to eat and do her business. Then I take the fake eggs and put in the real ones. Making sure she returns to the nest and settles back down.
The first hatch I kept removing the girls, but the second and third I let them regulate their own eating habits. I found I had to clean up poop no matter if I took them off daily or not. Be on the lookout for broody poo, it's NASTY smelling!
Yes the eggs should develop, but you can check them on the 7th day and see if there is anything growing. Use a bright flashlight or candler, if you've never done this do a search on how to properly candle eggs before.
So exciting! Keep us posted!