It depends on your home and living situation, but I would be the better person and tell them. It's hard to give them the opportunity to be the family you want them to be when you keep in them in the dark and never give them the chance. Be honest, invite them to celebrate with you, and if they shun you then oh well. You gave them the invitation and you were the bigger person who actually put the effort into family togetherness and unconditional love. But hopefully they'll end up surprising you and really consider attending.

It's better to have invited them and being turned down than not to do it and risk missing the chance to be together for your special day. Who knows, even if they decline to join you now they might come to their senses 10 years down the road and regret it. And that's far better than them saying "No, we had no idea she was getting married. It really hurt us that she never shared that and we would have come for it."

Good luck!!!