Bicycles on trains into Paris from Charles de Gaulle

By Taxi or on the Air France OR Le Bus Direct Buses you can put your bike, still in its shipping into the bottom if there is room. You might have to wait if there is no room

http://www.lebusdirect.com/en/

Also you could ride from deGaulle, or alternatively leave your bikes unpacked until you want to ride them—bring them into Paris in their boxes or cases or bags.

According to the SNCF and RATP websites, you are allowed to take bicycles on the RER during off-peak times (not 0630-0900 or 1630-1900 on Mon-Fri). So you are allowed to carry bicycles from CDG to Gare Saint Lazare if you take the route using RER Lines B and E. Only you know if you'll be able to safely take your bikes on escalators, though.

Note that Le Bus Direct services do NOT serve Gare St-Lazare, although you could take it to Etoile and get a taxi for the last part of the journey. Unfortunately, the Roissybus service to the Opera, very close to St-Lazare, does not allow bikes on board.

There are elevators at the RER platforms at Gare du Nord, and the RATP shows the route from CDG to Gare St Lazare with the RER B and E as wheelchair accessible, usually indicating elevators available.