Sorry I can't help with the trains to and from the Holiday Inn, but we took the TGV from CDG and the actual journey was only 10 minutes. We stood as it was a short time, which was tricky given our luggage and 4 year old. It was around 60 Euros each way for the 3 of us on the TGV.
Getting to Paris is very easy, the trains frequent and the people on the ticket desk speak excellent English and can explain where you need to go.
Sorry my answer is a bit light, hopefully someone else will do better.
Em x