Kelnstephen's 15 yo step son situation is different. I have two kids and in the past I have not taken the older one when his grades weren't up to the pre-agreed line. It was something special that was being withheld because of an agreement that he, himself did not keep.
Just an update on a situation near to this: for Christmas my dh and I decided to give our dn his first trip to WDW. He has had a very hard year with his parents splitting up after a very nasty and contentious marriage over the past few years. It's actually a Christmas present and surprise that he still doesn't know about yet (though his dad does) because we are the boring da and du that give him savings bonds for his birthday and Christmas every year so he never has anything to open from us anyway. The trip is planned for February 3rd and we just found out that he will soon have a new stepsister. Now technically, we could leave out the stepsister or her mom could pay for her to come but we have scaled back some things and rebudgeted so now she is also getting her first trip to WDW as well. We've still gone "all-out" for their first time including making shirts for everyone, making autograph/scrapbooks for the two newbies, making them pin lanyards and having everyone in the family that has previously been donate one pin to each of them to get them started, having a fairy godmailer sent out to be received right before the trip, etc.
Our dn will also be getting some much older step-brothers and they will not be going on the trip as they have their own lives going on and aren't really "kids" anymore.
