We would like to rent a bike in Beijing for 1 or 2 days.

For the official biks for rental, it is one for each, so you cannot share one. In order to register a bike rental card, you need to prepare your passport; transportation smart card with the sign of © and a minimum balance of CNY 30; a deposit of CNY 400. In addition, only those aged 18 to 65 can register the card. If your kids wanna experience the bike experience, they are suggested to rent at the private sites like Hutongs or some hostels.