I don't think Disney CA is 'out of her league'. She is getting this pension windfall from her ex, and the children will understand about it being a once in a lifetime things not to be repeated.
In our case I felt that 12 days in CA compared to 5 days Paris was much better value. With more children of course the economies of scale kick into play, and in both cases there are savings and expenses with more people.
In USA you pay per hotel room, in France like the UK you pay per guest, so a saving right there. And she wouldn't have to drive. I've been to CA three times with my son, and once on my own before he was born, this last occassion is the only time I hired a car, and as I said I wouldn't bother again.
For the two of us the whole 12 day holiday was at most £2,000 including flights, insurance, hotel, car hire, park tickets (6 days in Disney/California Adventure, 1 at Knotts Berry Farm and 1 Universal) and all our other expenses, food etc. I splashed out of clothes and shoes for my son as they were so much cheaper there too, that is all included in the £2,000. With three children you are adding another £450 for flights (I stress you must get the rock bottom prices in the sale), assume car hire will be replaced by bus/taxi, and then another £500 is more than adequate for park tickets and food. Hotel will cost the same for 4 as for 2, get one that includes breakfast and is close to the Disney park so no travel costs and you're away. SO I reckon that it would cost under £3,000 for 1 adult and 3 children for a 12 day holiday to California including everything.
What i'm saying is, if you're looking to splash £2,000 on 5 days at DLP then seriously look at a couple of weeks in California for not a lot more.
Balance up the costs, if you can't afford it then don't do it at all, the kids will have just as much fun at Butlins/Pontins, but will it be that lifetime memory? I'm saving up now to take my son to Disney CA again. It will be 4 or 5 years from now before I can consider it, but i can't wait!