I can't figure out why you both don't just show each other the cards you played??
I believe there are icons that say the opponent has to use sailing. With these icons you can directly show your opponent he cannot use something else (instead of proving it after the cards are discarded). But as long as your playing without cheaters, the icons are just a reminder I think.
and any card with a used trick must be played
What do you mean with played? If you also mean discarded, than this is not correct. There is a trick that let's you play zero cards. If the opponent attacked with sailing, you don't have to discard a card and can use the trick again.
I do believe it's the other way around: cards used in an attack have to be discarded(they cannot be swithed with a trick).