We're planning a family holiday to Ireland next summer. Ryanair is - of course - cheapest but is it better to pay a bit more for Aer Lingus? I'm worried that the kids rucksacks - although they will easily squish under a seat - will be 'caught' for being outside of their strict carry-on dimensions unless we pay to buy 4 new 'ryanair-sized' carry-on bags. Given this is a family holiday and we'll have lots of checked baggage, is it better to pay more and go with a more flexible airline? Cost difference is around £150 once we've factored in check-in bags.