This is how I handled my daughters party...I talked with build a bear and found out how much for a bear, one outfit and a pair of shoes. (Because I felt it was rude to invite a child to a party where you come to make and dress a bear...but only make the bear and not get to dress it.)
I also thought it rude to have parents pay for accessories on top of coming and bringing a gift.
I calculated the number kids I was willing to pay for and...
Then I told my daughter who was turning five that if she wanted her party there...and she did she, could only invite four friends. She was four and only had about four friends to invite.
The kids had a blast and were mind boggled they got to pick out an outfit and shoes.
Then we all walked down to the food court and had cupcakes that my husband has brought to the mall. He had gotten the tables earlier and had put table clothes on them, etc. Then we opened presents. Everyone went home and it was a huge hit.
We later went to a party there and the kids were only allowed a bear...I went in prepared for this and knew I was going to fork over about $30 on top of getting the girl a gift ($20-25). I told my daughter now six years old that there would probably only be a bear no outfit and if that was the case she had a lot of clothes at home. IF the other kids parents were buying outfits we could look for one but we might not get the bear one. EVERY child there was begging and pleading with parents for the extras...parents were not happy looking. My daughter looked at me and I told her we could find one outfit but no shoes today. She was thrilled and I paid for it. But I knew ahead of time...the parents that didn't were ticked.
So personally I would calculate how much you are willing to spend and give the kids a great party building a whole bear and not expect the other parents to pay for half the party so to speak. Good luck.