Your guest can buy a parkhopper, and this might be the
best buy, if she doesn't intend to do DD or any of the water parks. I'm just not sure about the LOS pass question, so won't say what I think the answer is (but I think it's possible).
As for the $$$ question --- I'd be prepared for a wide range of responses, and this is just my way of dealing with this. If I intended to invite people as guests, they would be guests, period. It would be wonderful if they took us out to dinner once or twice, and I might offer that as a suggestion to them if they persisted. Then they can decide how much they want to spend.
If the original discussion was to include them in the reservation and they would pay, it's a good idea to iron out all those details BEFORE the reservation is booked, so they know if the price is OK with them. Then you might take the total # of points X the general value of $10 per point and split that 4 ways. Not quite sure what you'd do when 1 person is only there 4 nights and the other is there the entire trip, however.
Unfortunately, $$$$ matters have a nasty way of leading to bad feelings when involving friends and family. When someone says they want to pay, but has absolutely no idea what the cost of the room might be, they could be in for a really rude awakening. It's difficult for some people to imagine the cost of the Disney rooms and they would never spend that much $$$ for a place to sleep. In any case, I'd never, ever try to go by the 'rack rate' that these rooms go for. That's not what we're paying as
DVC members.
Were you planning to get a 1 BR if you'd gone yourselves and are just getting a 2 BR because you have guests? Then you might consider the difference between the 2 BR points and the 1 BR points (ie, 34 vs. 28 points = 6 points for a week night) and multiply that times the general value of $10/point. Booking the extra BR might be worth 6 X $10 = $60 / night or $30 per person per weeknight. By having guests, I'd figure that I was spending 6 more points per week night than I would have planned to spend for just my family. (Still don't know what to do about the person who's staying the entire trip.)
I'm sure there's many ways to look at this situation, and you're the only one that knows what these guests mean to you and what their financial situation is. I'd probably play around with some of the math, and if the total just didn't 'feel' right, I'd probably lower it. If my guests thought it was too low, they could always give me more or treat me to a dinner. I'd probably try to keep it simple and not complicate this, in hopes that there's no misunderstandings about $$$. Good luck and hope you have a great trip home! We'll be there ourselves in May.