I have flown with my 3 children a good deal, from 5 months on in age. Both in seats and lap-held. If you lap-hold, there is a big commitment to holding the child. Flying to Europe with a little squirmer could be a disaster. For the low prices you quoted, it seems like a no-brainer to get the seat.

We are going to lap-carry a toddler cross-country in August. However, that will be with 4 adults and a 12-year old, who will all share the effort. That is 2 30-minute sessions each, with one for the 12-year old. Even that is worrying me, and it was to save almost $700.

Good luck. It is worth traveling with children.