I don't think Tesco deals are much use anymore - for a start you have to book a full price package.
If you want to stay onsite then book with Disney UK ( unless the £1 suddenly rockets

), wait until later in the year to see if they offer free dining - if you get a good deal then book it, you can always change if they do the 14 nights for 10 again next year if it works out cheaper - it has for some people but not others this time.
Best flight prices seem to be available around late November / xmas time - I got them for £320 each for late August this year - the schools seem to go back a bit later next year too - it's the 7th for Staffordshire according to the LEA.
If you want to fly Virgin then join the flying club, it will be difficult to get 10k miles ( 2k each for m+m flights) but not impossible - I've got 2k in 3 months just from Texaco star rewards - that is petrol for 3 people though.
If you can save £100+ per person on flights then it's worth spending £60 on buying extra miles if you need to - a Virgin cc for all your spending would soon add up too.
When I priced up the 14 night offer for 4 adults it was £3600 for a 1 bed suite at Old key west with ultimate tickets, if you reckon £1500 ( I think that's optimistic fr Mid August though) for flights that makes £5100 + food and spends of say £1500 - £2000.
Any flights earlier than about the 22 August will be double the price though, I'm afraid