transport options between airport Charles de Gaulle and Chantilly?

Steve can't help much with transport ideas,, I have relatives that I stay with near there,, but will encourage you to go to the Chateau,, the art is all throughout the rooms,, not just a "gallery" and it is AMAZING,, I have been 4 times and each time I really enjoy it.. The admission is for the Chateau,, but there are private tours that go into some rooms you can't go by yourself,, unfortunately they have always been only in french every time I have gone. I would contact hotel and ask them about what public transport there is from their location to Chantilly,, once in Chantilly you can walk or taxi to Chateau.

Chantilly is served by trains from Gare du Nord so if all else fails you can take an RER Line B train to Gare du Nord and then change. There are frequent but slow RER line D trains to Chantilly and infrequent but much faster TER services from the surface SNCF station. I've searched on the Oise departement bus website and there does not appear to be any direct bus from CDG to Chantilly.

There is regular bus service between Roissypole (at the CDG 1 RER station next to Terminal 3) and Creil. See the timetables here. It's a seven-minute ride on regional trains between Creil and Chantilly-Gouvieux. Service isn't as frequent as the RER B from CDG to Gare du Nord and the RER D from there to Chantilly-Gouvieux, but you won't need to go into Paris and back out to Chantilly. The bus between Roissypole and Creil stops at Senlis, a medieval walled town which would be a good additional place to visit. For information on the Chateau de Chantilly, go to the English version of the official site here.