That bit belongs to you - if going back there at the moment is too much for you, you really need to explain that to him and ask that he either covers for you or see if you can make alternative arrangements for your children. Can another parent take them for a while, can your husband take over for a while etc. Your girls may prefer it if you were there, but you're capacity to care for them will be compromised if you keep being retraumatised every time you go there.I have a really hard time holding up under pressure depending on who it's coming from.
Try not to hide behind your T if possible, this is something you need him to take care of because you need to feel safe to process what's happened. Rather than thinking of it as putting yourself first, think of it as allowing yourself to heal. Would you feel the same fear if you had broken your leg and couldn't drive them there? What would you do in that case? It's the same thing here.