i think the jumbo in black caviar is one of the most classic bag you can ever own. It's a stunning bag and i would love that to be my next purchase! I think you made a excellent choice! I love the beige as well, so i can't say that you shouldn't exchange it for a beige one. But think you should be so so happy for your new bag! It will always be in style and perhaps the black will suit your lifestyle a bit better since you have children? And maybe the beige flap is better in the medium/large size! I would love that one in beige and the jumbo in black!
You have to post pictures! I really really hope that you love your bag, and you should always do what you want to do. But i think that bag is such a great choice!
Congrats to you