Riding mowers are basically lawnmowers with a smaller motor. It can be used on both normal lawns and also on heavy, kiddie-sized lawns. The best part is that they are portable - it takes less than a minute to set one up, and you can use it wherever you want, even if there is no grass present.
In the Riding Mowers category, Best Tool Box has summarized a lot of advice and choices for you. You will not have to worry about investing a large amount of money in vain.