Viva Aerobus has several different destinations; however, you can still use the airline to travel within the country, if you want to travel through Mexico you will need your passport, voter ID, driver's license, professional ID or consular registration certificate. You will not need all of them, just one of the following, with a recent photograph of yourself. 

If you are traveling outside the country, you will need to show a valid passport and the necessary immigration documents required by the country you are visiting. If you are going to the United States, you will need your Visa, residency permit or electronic system for travel authorization. In Canada, you need your Visa or an electronic travel authorization. For Cuba only your Visa or tourist card. 

Yes, if you need a wheelchair to get around, the company will offer you assistance free of charge at any airport where they are present. You can also bring your own wheelchair and they will transport it for you free of charge, but don't forget that if your instrument uses batteries, they must be sealed or disconnected.