A Paris city break for a wheelchair user

It’s my mother’s 80th birthday next year and I’d like to take her on a European city break to celebrate, such as Paris, Rome or Florence. She is confined to a wheelchair with Parkinson’s so I need a mode of transport and a hotel that will be easy to access. Can you wheel someone onto the Eurostar to Paris in a wheelchair? And which hotels are a) central and b) wheelchair friendly, also with disabled bathroom facilities? What would you recommend?