There are a variety of ways to level the playing field in chess. The two most common methods are material advantage and time odds, although there are also a number of more exotic handicaps that one can conceive of (e.g. giving away free moves, requiring a given piece to give checkmate, allowing the King to move two squares, etc).
With material handicaps, you give up some of your pieces, to the advantage of your opponent. This type of handicap has the advantage that it is simple to tune, and can be easily adjusted to correspond to the difference in strength between the two players. This form of odds was very common in earlier centuries, prior to the invention of the chess clock.
The main disadvantage to material handicaps is that a game played with such a handicap is quite different to an equal game. Without a Rook, for example, one cannot castle on that side. Strategic decisions may also be skewed by the weaknesses arising from the missing pieces. For example, you might prefer to focus your efforts on the side of the board missing your opponent's Knight, simply because the piece is absent. In this sense, one can argue that strictly speaking, the game you are playing is chess-like, but it is no longer chess. So there is a philosophical argument here as well - material handicaps are inelegant, and inherently unfair.
With time handicaps, a chess clock is used to disproportionately limit the thinking time of one of the players. For example, you might play with only two minutes of time, while your son has, say, 15 minutes. This effectively limits the depth of your thinking, without changing the conditions of the board itself. Time handicaps are preferred among chess players with even a little skill, because they do not change anything about the game itself, and they allow both players to have a satisfying experience. Psychologically, time handicaps feel more fair than arbitrary material adjustments. However, playing against a clock is a skill in itself, as is making effective use of the extra time you have available. This makes time advantages less effective for chess beginners.
Recommendations: For beginners and children, I would start with material advantage. It's easy to do, and children can easily understand the advantage ("oh, you don't have a Queen!"). As they improve, you can steadily reduce the advantage, until ultimately if all goes well you will be playing on even terms. The problems of material handicaps are just not an issue when you are still learning the basics. Equally important, having more time is not much help without reaching a certain minimal level of competence. You need to know what to think about before being given extra time to think is helpful. Once you have a bit more experience, consider moving to using a chess clock with different time limits for each player.
