I'm no expert on baggage rules but I'd definitely look for further confirmation as aer lingus seems to have a different baggage policy for infants in only allowing 10kg of extra checked baggage not a full 23kg.
Also the 23kg each I think refers to each bag and you can't combine the allowance into 2 bags if that is what you are suggesting... But I'm not sure maybe with infant allowance it is different
BA forum might be able to answer this also, tends to be more active.