How Do I Invite Others and Ask Them to Pay for Themselves? Need Advice

I don't think it's tacky at all... if you aren't sending out gilded invitations or anything. I mean, it's just family. Spread the word verbally that you are going to dland that day to celebrate your daughter's birthday, and anyone is welcome to plan their own disneyland trips for that day too if the time is right for them. Make it low-pressure, disneyland is very expensive with a family.
I know in my own family, we love to get the cousins together, and if one family was going for their kids b-day, we would probably be more than happy to join in and pay for our own trip at the same time just to make it a party and a memorable experience for the kids.
I just don't think you can send out any formal kind of invite for this, because then that implies you are hosting. You just have to tell folks that you are taking her for the first time and that anyone from the extended family is welcome to join up with you at the park. Also say that you totally understand if they aren't in the market for an expensive all day trip to the theme park at this time. I don't know anyone who would assume that by saying it that way you are planning to pay their entrance fees.

Send an e-mail out saying....We are celebrating so&so's birthday at Disney land,for those of you who would like to join us. I would take some cupcakes in the park with you. Or they have really good ones at the Candy store on main street. To share with those who do come. Prob a good idea to make sure they know your not buying them tickets. J.

Hi I.,

About 1 years ago we were invited to Disneyland to celebrate my nieces B-day party, but we were not notified that WE had to pay for our own ticket (family of 4). It put us in a predicament because we made the assumption they would be paying for everyone they invited. Well, it turned out they paid for some and not for others. That was very tacky.

In your situation, I would have your husband speak to his siblings and explain that they are more then welcomed to join you in celebrating your little one's b-day at Disneyland and since they have to pay for their own ticket - you don't expect a B-day gift, their presence will be more then enough. What's more important then family. That's what I would do.

Have a great time.

~B.

Be straight up with them. Tell them " we're going to celebrate my daughter's b-day, and we think it would be fun to meet up with you. Unfortunately we cannot pay for your entrance, but we are more than willing to buy the cousins lunch, or a cupcake or a small souvenir as a reminder of how much fun they had....."

If my relatives were to tell me this, I would completely appreciate the fact that they want me there. I would also truly understand that they cannot pay everyone's way into the park.

It would be totally tacky to invite them to join you, then ask them to pay for themselves. Just take your own family to Disneyland and have a great time. You could always invite everyone over to the house just for cake that evening or the next day.