My flight in May lands at a similar time. I didn't want to risk the last TGV, I can't remember exactly when it leaves but I felt like it was cutting it too fine. I booked a transfer with Rideways as i've used them in other countries and got on fine with them. There may be cheaper alternatives but I'm not sure who.
I normally take the RER, it's pretty straight forward but it takes a while compared to a car transfer. And i'd be the same as you, that time of night and with a 6 year old, you'd be better off with a transfer.
It's one less thing to think about once it's all booked.