I'm afraid that on low cost carriers, they will permit families to be split up. It is free for all boarding for a reason. Occassionally they may allow disabled pax onboard first, and even more occassionally children, but it is usually done as first checked in, first allowed on, so allowing all the families on first would negate that.
They usually try to get round it by asking people on board to move seats so kids can sit with parents, but you do get A&*holes who refuse. In which case, i totally endorse the reminding of these people that your child will be crying and may wet themselves if you arent there to take them to the loo.
Unfortunately, the contract you have with the airline os for them to get you from point A to point B. As long as they do that somehow (and it doesnt have to even be by plane or on the same day!), they are not obliged to seat you togther, even if you have children, so CAA recommendations are unenforceable.
Which is why if you really want to sit with your kids, its better to fly with a decent airline that offers preallocated seats, usually preseating families with kids before you even come to the airport.