@ edryer4356, you really should have started a new thread with your questions for a couple of reasons. People may miss your question and if they do answer it will throw the original poster's thread off course. I am going to risk that now and go ahead and answer to the best of my knowledge.
"How much time do we need to leave ourselves for a train departure?" 3 to 3.5 hours between scheduled arrival time and departure from Orly and typically 4 hours from CDG.
"Would an 11am train be cutting it to close?" Maybe not because you will not have to go through passport control. I think 3 hours might be enough.
"Or should we fly into Orly?" Taxi from CDG to Gare St-Lazare train station is a fixed rate of 53€. Taxi from Orly is 37€. The rates are fixed and are for four passengers and their luggage. Mass transit is easier from CDG. The taxi ride is just about the same if there is no traffic. Which route is more likely to have traffic on any given day is something that maybe a local person will answer,