SS, it's not unreasonable for it to be beyond the scope of your imagination at this time to be accepting of your STBex's GF. You haven't even gotten to the point of accepting that your M is probably over. Don't be so hard on yourself and don't try to bite off everything at one time.
The only thing I would suggest is to not burn any bridges in the meantime. I think it was our Abraham Lincoln that said, "Keep your friends close and your enemies closer." It's not important for you to imagine it now, but in the future, your acceptance of the situation and her will make life easier for you and your children. Again, I'm only speaking from the experience I had with my H's ex, and the trauma she inflicted on everyone, including her children.
It's really too far out in the future for you to be thinking about this. You don't even know if your H will be staying with her. Focus on you. Don't cut off your nose to spite your face regarding silly material things like camping gear. It's so unfortunate that you weren't afforded more time to get used to being separated before having to deal with the OW too. It is tough and you need to be patient with yourself. (())
