There are a couple of accommodation options in resort that cater for visitors with disabilities, mainly Mercure Hotel and Chalet Mounier. Please enquire directly with them for specific details.
The lift offices offer a substantially reduced pass for disabled skiers, plus a free one for a carer if this is required. You need to take some kind of proof of your disabled status – French people have a disability ID, and the ticket office staff will want something similar in order to justify the sale. If you need a carer, they’ll look for some sort of justification for this as well.
If your disability is obvious (eg wheelchair user, Down Syndrome, loss of limb etc) there should be no question, but the cashier will clear the sale with a supervisor first.
Sit-ski access is restricted to certain lifts – ask at the ticket offices for details. You can definitely use the Jandri Express, which gives you access to most of the resort’s main pistes.