You could stay at Wyndham Bonnet Creek in a 2, 3 or even 4 bedroom condo for less than what a Disney moderate costs. You can rent weeks through brokers like Vacation Upgrades or Vacation Strategies, Farrells Vacations, Shelby Resorts, Aaron Washburn for very cheap. The condos have a full kitchen and washer and dryer.
The resort itself is on Disney property and has 5 pools, 2 slides, 2 lazy rivers, free putt putt golf, activity center, craft room, game room and have things planned for kids all day long like a make your own ice cream sundae every day at 3 pm.
Here is a pdf booklet that shows the list of activities they have for kids every day.
https://www.wyndhamvacationresorts.com/ffrweb/pdfs/BonnetCreek_AG.pdf
You can buy an Orlando Flex ticket for around $300 per person that gives you 14 days at Universal, Island of Adventure, Wet and Wild, Sea World and Aquatica. You can add Busch gardens to that for $30 more.
http://www.orlandofuntickets.com/Flex-Tickets/
But to be honest...to stay 14 days for 5500 pounds is a pretty good price.
We usually do Disney parks, and Universal parks, as well as water parks and other things like Blue Man group or Cirque Du Soleil and our family trips for 10 days usually cost around $7,000US.
You can rent a condo in a 2 bedroom for around $100-$125 a night and a 4 bedroom for around $225 a night.
There are enough activities just at the resort that you could spend a day or two just doing the resort activities. Depending on how old your kids are.
If you have a kitchen you could make breakfast in the condo and save money on that. You could make some dinners like a frozen Lasagna or frozen Pizzas a few nights and save a ton that way.
The kitchens are fully equipped with pots and pans and dishes, etc for cooking.
The only difference staying there is you have a ton more room but you do not get daily maid service. You get it once a week.