That's the WORST thing he could do. Way to start an argument and HIM look like the jerk!If not, let your ex-wife know that you feel it is time your child and your wife get to know one another better.
OP, let mom know you will be exercising your weekend overnights immediately, as per the custody agreement. Let her know you will file a contempt charge if she REFUSES to allow YOU your overnight visitations with your son.
Pretend there isn't even a new wifey involved. Its YOUR right to overnights and has NADA to do with new wife.