I know why you called him Luke! So you can say "Luke....I AM your father...."
Congrats and glad to hear everyone is doing well. The best advice I was ever told about having 2 or more kids is this. When feeding, holding or doing anything with the baby you are 100% engaged with the other child. So if you are feeding him, make sure you are talking to your daughter (making eye contact as much as you can) so she is less likely to be jealous. Good luck!
Geoff