As of right now, she just gets it. I have 100% trust in her - we have a very, VERY close relationship and see each other all the time and she loves my kids almost as much as I do.

In fact, I've had serious conversations with her about spending MORE of my money if dh and I pass...she is very frugal, barely spends any money and I have fear that she will be afraid to spend any of my money on herself or her kids. We would be leaving them quite a bit...and aside from paying for my kids college and giving them a nice down payment on a house and/or wedding costs, I don't need my kids to have a huge lump of money...so I have encouraged her to use our money to pay off her house so that she can quit her job (with 5 kids 4 years apart, makes sense or she'd go nuts), to fund her own kids' college funds with it, and to take some vacations with it (she is not a WDW nut like me, so I've encouraged her to do some WDW trips in our memory).
My husband wants to make some changes and setup a trust. I am unsure exactly how that works and how easy/difficult it would be for my sis to get some of the money to spend on just 'everyday' things that cost more with 5 kids as opposed to 3...like vacations, bigger vehicles when it's time to buy a new car. I think how it'll end up is that SOME of it will go into a trust...and some of it will go directly to her. Like I said, I have no desire for either of my kids to get $250,000 handed over to them when they turn 21 or 25 or whatever...Especially since I won't be around to make sure they are responsible enough to handle it and not just piss it away.
Any advice on a trust??