I have a "dad" that ran out when I was 4, because it was convenient. When I was 15 we met again and it was gonna be this "great father-son relationship", but the reality was he was just some old guy who I knew gave two fucks about me, and I was just some shithead kid he was trying to use to void his guilt. Shortly there after, we parted ways for good.
In his mind, he's just talking about meeting up, but he really wants to do this same thing. The problem is that even if he's a super great old guy who had fucked priorities with his kids, you'll always resent him for what he did. End result means don't meet with him, but tell him (by answering the phone) that you aren't able to let strangers mingle in and out of your life as "family".
Once you have sons (as I do, and you may- IDK), you realize just what kind of coward would have no relationship with his sons, and come up with some petty excuse like money, etc..
As for my dad, he can live and die with his faults, and so will I. Running out on my sons won't be one of them.