Her kids are really excited about the wedding and she keeps telling me how they cannot wait to see me get married. Since my mom is helping with the planning she knows i do not want kids there and she let it slip to my sister and my sister got mad. I told mom to tell her that the site will not allow kids to come, though that is not entirely true. Now my sister is saying her feelings are hurt
Of course her feelings are hurt. She kept telling you how excited her kids were and you never once corrected her. And apparently, you planned to keep lying to your sister because you state that your mother "let it slip." Then you tried to get your (and her) mother to lie to her.
sister is a bridesmaid, so she should be at reception
Why?
You are entirely within your rights to have an adult only reception. There is nothing wrong with that. You do not have to invite any children, whether they are relatives or friends. It sounds like a fun party and one I would enjoy attending.
However, when you set rules like that, you have to know that not everybody will be in a position to be able to follow them.
Your sister has told you what she is able to do within the parameters of your rules.
She can attend the wedding, but not the reception.
Sounds like a great compromise. I don't see why you are stressed at all. Your sister will be there for the important part, witnessing your marriage. She just won't be there at the party after. Not a big deal, it is just a party. She will be there for you for the marriage.
Oh, and I agree with everybody else. The minute she told you her kids were excited to come to the wedding, you should have been upfront and told her right then and there that you were having an adult party. By your silence, you tacitly acknowledged that the children were invited. How did you respond to her when she told you her kids were excited? The only proper response would have been to say "Hey Sis, I think there has been a misunderstanding, we are planning an adult reception." Your lack of correcting your sister's assumptions and remaining silent when she told you of her childrens' excitement only served to confirm that her children were actually invited.
I don't buy the "I was too busy to tell her" when you obviously had the time to plot and ask your mother to lie to your sister about the whole thing.
Continue planning your wedding. It seems to have been resolved already.
As for your title, this is not your sister's wedding dilemma. She is doing what she can to accommodate you the best she can. She will be there for you for the special and important part, the wedding, but then needs to go home with her kids.
This is your dilemma because you want your cake and eat it too. You want your rules and you want everybody to arrange their lives to accommodate you. That doesn't happen in the real world, bride or not.