I have been doing indirect for about 18 years, approx 20 times. Thankfully not one problem, yes a slight delay, a rush thru immigration etc but always got there and saved £1,000's.
Saying that we have only ever done it with 1 child, personally I would do it with 4 but I am sure others wouldn't.
You need a minimum of 2 hours, I have done it under the hour many times but you need over 2 hours if never done it before, if you are a worrier go for upto 3 hours. In this time you go thru immigration, collect luggage and re-check.
Coming home anything above 1 hour as you don't have to do anything but get off one plane, possibly change terminals (not always) and get to the next gate, no immigration and you don't see your bags.
Prices are up and down a little this morning but just looked at 2 adults & 4 children.
Direct £7,866
Indirect £3,714
Over £4,000 for the sake of changing planes, surely even the most die-hard direct fan would have to consider indirect.