Best thing is they go home after a day with you; LoL visit and leave.
I'll never see it start my family too late, Girls are Daddy's Babies and they both would make wonderful Mothers but that going to be their choice is get married and start a family. I'm in mid 50's and climbing so maybe Grand dad but great grand dad that will be reaching.
Enjoy and spoil and send back home is your new job !!!