it means, 'hey kids(or guys), it's a dad here.(or can use i'm a dad.)' the second sentence has no subject. 얘들 means guys who is here.(literally) 아 means hey and 아빠 means dad.(to be exact, 아빠 is an informal expression. of course not rude.) 야 means... Hmmm.. i guess it just means 'it's'. hope this helps. :)