I guess an April fool gambling site will end up fooling everybody as they will not be found in the hot wallet to pay for players winning only on that fools day so let's say the gambling site just fooled you to make deposits make a bet and after winning you discover it an April Fool winning.
Nah, they will probably pull the pranks off at the end when players win or something like that then telling it's all just a prank jokes. But so far I haven't seen any gambling sites offer such or make a joke about it. Maybe it's not that funny or it's not that good to pull something online that might cause player a false hope or added stress when they find it out.
Anyway, I think they were aware of the facts that financial problem is not a joke or some kind of situation or works is not worthy for pranks. Besides, gambling addiction is never a joke so I think that was it or it depends on the casino.