I think it is extremely rude for them to exclude you from the picture but allow your husband and kids!
I think its RUDER if they dont want you in the pic. because of maybe a future divorce!!!
I am sorry, but that is just stupid, oh wait, i've got an idea.....
why dont they also exclude the groom because you never know, they might get a divorce later on and you wouldnt want a pic of your wedding with your ex-husband now would you????
Family is family, and its just disturbing if they have this wall up because you arent a blood relative. I would understand an immediate family pic, like mom, dad and the kids but its a completely different thing when they allow the kids but not the spouses.