Are you isolating from other relationships and connections as well? Or is it just the church setting?
It's not really useful or accurate to call yourself a bad parent for not going. Seems like this is simply part of the battle with PTSD holding you back.
The thing with avoidance and isolation is that the more we avoid and isolate, the worse people will feel over time. The worse symptoms will get. The solution isn't to race towards what we are avoiding and jump in, but to shift the pattern. Take a step the other direction.
When I get really avoidant of connections, I carpool with others. The commitment to someone else gets my butt out the door. 75% of the time, I end up going rather than canceling simply because canceling would take more effort. For awhile, I signed up to hand out bulletins just to get myself to go.
I don't really have any suggestions or advice, as I don't have kids or a family - but I can relate to liking the people and the church and still struggling to get myself out the door to go at times.