I make smaller cards on the computer - they're credit card-sized, and I laminate them. Because they're so small, they fit very easily into the small wallet I use when traveling. I measured a credit card and made sure that the dimensions of my cards were just slightly smaller than a credit card.
I put the following on my cards: park hours, parade/fireworks times, EMH schedule. And I also put trip specifics on one: ADRs, confirmation numbers, and phone numbers (cell phone numbers of all travelers in our group, town car phone number, hotel phone number, WDW dining phone number). I also make one card that tells which park we plan to go to on which days.
I don't make one for each day -- I just put the info on the front and back of each card, then laminate them. I think that for our trip in October, I made up four cards, front and back -- then laminated them. You can use a pretty small font and get lots of information on there.