I’d echo the advice. No problem doing it. I have done it just recently. You will have to call to book the award for the children but they’ll waive the fee.

Imho LH is the better experience with Kids. They give them toys and stuff while UA may or may not give them a pin...

We also a while ago were fortunate to have empty seats next to us when traveling with lap
infants in LH C 747 Upper Deck which was great as they let us let the kids sleep there.