IMO, your AC should invite all parties and let whoever will show up. If your X doesn't want to be around your current DH, your X could choose not to come. Or he could choose to be there for his DSs and GC and never mind about your new DH.
But, clearly, that's not the case. I totally get it if you wish to stand by your DH and not attend events where he is not welcome. However, you might want to make an exception for milestone events or, at least, your GC's events. After all, it's not their fault their dads feel this way. Would you feel comfortable leaving DH at home to be there for your new GS at his Christening? Would DH be ok w/ it if you did?