Should I attend the wedding of a close family member who has told me not to bring my children?

My niece, whom i helped to raise after her mother's death is getting married. We were so excited to attend the out of town affair and bring our children who don't get to see family often. Today i received a facebook message that let me know that children were not welcome and please don't bring mine. i understand that they are envisioning a care-free adult only event. I am so sad she does not want them there, they are an extension of me. Plus obliviously at an out of town location, there is no one i would leave them with. She said her mother-in law to be who lives there could find someone trustworthy, but my kids have never been left with a stranger. I can't even imagine enjoying this event without them. I have read several wedding etiquette sites that say it is becoming more acceptable these days, but i simply don't agree. I can see if it was some other type of affair, but a wedding? I feel like i can't win here. I either strand my children with someone whom they are uncomfortable with or i greatly hurt the feelings of my family by not attending the event. My almost 20 year old step-daughter who still lives at home with us has offered to stay at the hotel with the kids and miss the event, but i hate to think of her being set apart once again. It is already hard enough for her being an outsider with the rest of the cousins who have been together their whole lives. Side note: If you are planning a wedding event, and you have been wondering if it's ok to plan an adult only event i am going to say this: Of course you can do whatever you want, after all it's your day. However, if you think you can do it without offending and hurting others, you can't! But if your uninterrupted perfect day is more important to you than the feelings of others, go ahead! You better make sure you stand at the bar and head off anyone who is overindulgent as well. I have seen more uncomfortable situations with tipsy or downright drunk wedding attendees than i ever have with children.