I have always struggled to make sense of the Trinity. Even more so when I have tried to explain it to my kids. I came across this that helped me and my kids:

 

Athanasius compared the Trinity to a lighted candle: the lighted candle is a flame; the flame is light and the flame is heat, but it is all one flame. The One God is the creator of all, the one God is the incarnated light of Jesus, and the one God is the warming presence of the Holy Spirit. All of these manifestations are at the same time the flame of the lighted candle. This remains the best analogy I have found to describe the Trinity.

Rufus H. Stark II, retired Methodist minister, writing to The Christian Century.