i dont know its a bit of a sticky situation! but IMO i would go ahead with it, after all it is your DD's bday and she deserves to still be reconized. I think if you just let family know your plans and remind them not be feel obliged (sp?) to come all should be fine. (i hope)
Some might accually like it, get there minds off it and enjoy being around family.
After all your DD is still a family member. Just dont be offended if they dont turn up

Good luck with your choice and wish your DD a happy bday