1
I hid my disappointment when the trip was canceled.
Sign "disappointment" by tapping your chin with your index finger, then use signs for "hide" and "cancel". Your facial expression should shift from disappointed to neutral to show hiding the emotion.
2
It was a huge disappointment.
After signing "disappointment", you can emphasize the intensity by making the movement slightly sharper and exaggerating your let-down facial expression to show it was a "huge" letdown.
3
Are you disappointed in me?
Point to the person, sign "disappointment", and then point to yourself. Make sure your eyebrows are raised and your head is slightly tilted forward to indicate a yes/no question.