I quite like the calculator that Gillingham have used.
Family ticket, 2 adults, 2 kids - £88.00
Individual prices
Adult - £23 x 2 = £46.00
Child - £11 x 2 = £22.00
Total if bought seperately £66.00.
So if you bring your family then your going to have to pay another £22.00
Wycombes not much better, they offer NO DISCOUNT for bringing your family, but I suppose they aren't charging you extra!