Two little ones

So me and my boyfriend have been together a little over a year,and yes we are ttc..our problem comes in at explaining to our daughter's(both previous relationships)he's Caucasian and I'm African American. Our daughter's love each other and we recently told them that we were planning to have a child together..this is where the questions came in.his daugyers five mine is four..is it to early to explain how things work?also they are really confused about what color the baby will be.Lol his daughter says white mine says black.Lol..it's pretty funny but they are very serious with their questions and ask all the time..any thoughts on this ladies?