http://www.thenational.ae/business/t...via-careem-app and related articles linked from that page.

Some background. There are no legal self-employed drivers in the UAE, unless they have spent a fortune to create their own company. So Uber et al sub-contract to other legitimate limo companies. Further, they are required to charge 30% above the govt regulated/metered taxis.

What trips will you need to make ? Maybe we can give you an idea of how much cash you would need. Airport taxis should accept cards; ask the dispatcher when you join the line.