I have not read all of the responses. When I was a teenager, 25-30 years ago, I invited friends on a few different Disney trips. We traveled in our van and camped at Fort Wilderness, so transportation and lodging were obviously covered by my parents. We had many meals, snacks at our campsite, this was all covered by my folks. My friends had to pay for their park tickets, and any meals in the park as well as souviners. Once I knew what friend I wanted to invite, my mother talked to my friends mothers, without my friends knowledge. My Mom had already figured out how much money my friend would need. Everyone seemed happy with the arrangement and we all had a good time.
For my boys, we have never invited friends on our
Disney vacations. However, if we did, I would do the same as my parents. I have been a SAHM for 18 years. Over the years we have literally brought my boys friends with us on hundreds and hundreds of day trips. Kids started joining us when my oldest was five. Initially I planned to pay for all the outings for everybody. (I was young and naive!!!) We went to a childrens museum. I paid the admission, we spent the day, had a wonderful time. As we were leaving we walked into the gift shop. My sons friend pulled out a $20.00 and bought himself all kinds of cool trickets. We didnt buy anything as I had used our money on admission. Two days later we brought another friend to a waterpark. I paid everyones admission. At the end of the day, the same thing happened, friend spent a bunch of money in the giftshop. From then on when I invited a child with us, I told their parents how much the admission would be. We have done this for the past 13 years. We have never had a friend not come. In fact over the years, I have had my boys friends parents, give ME gifts for all I have done to give their kids such fun outings in the summer. Of course many of the places we went were free, and in those cases of course no money was needed.
I think for me the only time I would have felt differently about kids paying their own way, was if their family had invited my kids from time to time and paid my kids way. However, since I have always been home and run our summers like an activiity director and ALL of my kids friends parents were working and unavailable to do day trips, it was always me bringing all the kids. When I say we have done hundreds and hundreds of day trips over the years, I mean it. We simply couldnt have done so much if I was ALWAYS paying for extra kids. However, what always stuck in my head after the first two trips was that is I wasnt paying for somone elses admission I could use that money to buy my kids a tricket from the giftshop like the friends had done.
Honestly though, My kids friends parents have always been very appreciative that instead of their kids sitting at home all day, they got to do some fun stuff with us. It made a little more work for me to have extra kids along, but was always worth it and we have had some remarkable adventures.
To the OP, I say to talk to the friends parents with how much money they would need. Most people are not looking for a free ride for their kids and are just happy that their kids are included in a fun outing or vacation. Good luck!!!