I see this as a marital issue, not a step parenting issue.
It's sometimes easier to focus on kids doing things instead of dealing with husbands, but I don't think this issue will ever really be solved until you and your husband discuss his involvement in the family, especially as you are bringing additional children into the mix.
Having children is both a joy and responsibility. It sounds like your husband needs to rethink his outside obligations so he can parent the children he has helped bring into this world.
nak (baby was born thursady!)
It is a marital issue, as we disagree, but also a parenting issue as DH wants to make sure dss & dsd get lots while they are with us (read- alleviate his guilt for not being there for them daily) but doesn't/can't assume the responsibility for making that happen.
i think i really need to remind him of how we treat the kids in our home- and make that our baseline.
i wish he would rethink his outside obligations/choices but that i believe needs to come from his desires not mine. guilting or forcing him into a change would not be very productive IMO for us as a couple.