After we did the sinus rinse on my son – his ear became plugged and now is draining – is that normal?

If your son does not have any blockage in his nasal passage and air can pass through, it is possible he had his head in the wrong position during rinsing. If it is tilted too far forward the solution may go in the ears. This is not harmful and the problem should clear up on its own. Please make sure that he blows his nose gently after rinsing to avoid putting pressure on his eardrums.