Customs time with checked luggage

Patricia, No, it won't make any difference. Customs does not take any time, just walk through the green "Nothing to Declare" door.
What does take time (1 hour is not unknown) is immigration (passport control) which takes place before you pick up your bags. So your bags are waiting once you get through immigration, and you can then walk through customs without stopping.

Hopefully you luck out like I did last May. It took longer to walk to Immigration than it did to process through it, 5min. We had to wait about 20 minutes for our luggage.
Enjoy your trip.

It all depends on how quickly your luggage is unloaded.

You don't go through Customs, but depending on how many tour groups are in front of you in the Passport Control line, there really isn't any reliable way to judge your time.

I am Really concerned about waiting for our luggage. We usually do carry on and that is my big concern. We have already purchased the train tickets. Maybe others on the plane would be willing to lift our luggage for us?

If your plane arrives on time, you should be perfectly fine timewise -- even if you have to wait for your luggage after you go through immigration to pick up your luggage before heading to the train station in the airport. (If your luggage isn't there already when you come out, usually 20-30 minutes is the most additional you would have to wait.) Three hours is a decent cushion.

There are always exceptions, crazy days, etc., but in general, three hours should give you enough time.

I am wondering though about your ability to manhandle your luggage on the train as well as on the plane. Do you still have some range of movement and strength in the suspect shoulder(s)?

Patricia, you are sort of implying your luggage is hand-luggage size, but you are not up to putting it up in an overhead rack. That could also imply a problem on trains. I hope it has wheels, so you can pull it behind you and up and down escalators.

You will have to carry your bag yourself onto the train. There may be 2-3 steps up to the train, or steps inside the train if it is a double-decker.
Best picture I could find of the steps into a TGV: http://farm5.static.flickr.com/4137/4887091293_2fa71399b6_b.jpg

Inside the train the racks are no easier than on aircraft, so you will need to put your bag in the racks at the end of the coach, or in the A-shaped space between seat backs.
For details about luggage on trains, and photos, see here: http://seat61.com/luggage-on-european-trains.htm

This is not specific to CDG, but every time I've had more than a 15 or 20 minutes at passport control I've had little to no wait for a checked bag. I'm guessing that while I wait for passport control my bag is being processed too (scanned, paperwork, dogs, etc). I can't recall a time when I had a long wait at both passport control and the luggage carousel.

Thanks for all the advice. We have carryon luggage and I have no problem with my shoulders. But I am in my 70's and I am too weekto lift my bag to the overhead. My husband has always done that. He too is in his 70's and is having shoulder troubles. We planned this trip before the shoulder problems began. From your advice I think we should just check our luggage in Denver and hope for the best. timewise. We are active seniors but this setback has us concerned. Thanks fir all your help. I am sure we will be fine....

I always check my bag and I almost never have to wait for it in Europe. By the time I get through immigration, it is typically on the belt.

Regardless, make sure that you pack a change of clothes and any essentials in your carry-on just in case your bag goes missing.

I'm your age and have traversed CdG enough times to think that you can relax, with your bag checked. It's impossible to predict the unpredictable, at CdG or any big airport. So expect to lose some time. First, arrival is when the plane is on the ground but it may taxi for what seems like forever to the arrival gate. All the passengers will fidget until shuffling into the terminal. The security and immigration line-ups are one of life's great mysteries. But while you are standing there, your checked luggage is being sorted. Keep your eyes peeled for an ATM machine to obtain euros. Once the bags tumble off the conveyer, you face a slim chance of a spot customs check, but probably not. Then follow the signs to the TGV station in Terminal 2 (not the adjacent RER suburban train.) The airport website will help navigate; you can determine your route from the United gate and print out a map (or smartphone). One warning: You have to carry your bags onto the train, where luggage space is tight. Some TGV trains are double-deckers and your seat will be assigned, perhaps upstairs, although I don't know if this will be a challenge on your route. Even so, three hours should be comfortable enough to have a morning coffee and croissant at the train stop.
PS: The Avignon TGV station is on the outskirts with a short train shuttle to the old station in town. By that point you might want a taxi to your hotel.
http://www.parisaeroport.fr/en

I assume your train to Avignon is from CDG. If it is from Paris then you will have a tight squeeze to make it especially if you end up in a 90 minute immigration line which is possible although usually you are through in an hour or less..