i wrapped each gift in a colored "lunch bag" and had stickers that i printed off my computer (in disney script, of course) and left them on the table each night after the kids fell asleep... it was great fun hearing the kids thanking the characters who left them a gift (each day was from a diff't char) and asking how they got into the room w/out them hearing them and with the doors double locked... it was one of the highlights of our trip!
now, if you are not staying in the same room, you might want to take an adult from each room into your confidence and have them be your magical helpers to plant gifts each night/morning... another option would be to have each day's gifts in a bag (marked w/names if it matters) and distribute gifts each morning before you leave the rooms or at breakfast (saying that it was left in your room/on your door)... i definitely think one a day would be better than all at once... makes it more special... esp if you coordinate it w/the day (underwater camera for water park day... water yo-yo w/a note from tigger [tiggers don't jump, they bounch] on the day you're going to crystal garden... glow sticks/necklaces for a parade or fantasmic night, etc)