ok, probably too late now but here are my tips: (remember you only need to score 50 points/50 np for credit.)

dubloon disaster: grab 2 coins, so you have 2 mines following you. position yourself halfway between them with room to run and wait. once they get close, slowly move forward, keeping just out of range of the mines. the mines will collide and blow themselves up. then grab 2 more coins and repeat. it takes a while, but it works.

extreme potato counter: erm. well. i know people have used videocameras to tape it, then played it back in slow motion and counted 'em. i've never scored above 80 or so. you know those pictures that if you stare at 'em the right way, another picture jumps out at you? ok, i've never managed to see the other picture, but if you watch the potatoes the same way, it helps - stare at the center of the screen but kind of don't focus so you can see the whole thing. don't look to one side or the other.

faerie cloud racers: yeah, not stellar at this one either. you start at the left, moving right. the other racer will be moving towards you. usually they move up one and then continue right to left. so, go down one and then continue moving left to right. then go up at the right edge until slightly above the level of the other racer and start heading back to the left. your goal is to box 'em in.

jolly jugglers: this game usually p*sses me off. stupid little chia things. remember that you have 100 health points per guy. each time you get hit, the active guy dips by 25 points. so, if you're making a jump into a bunch of villans, start with the guy with the most health points left. and make sure to collect the fruit when you kill 'em. actually, some of the bad guys regenerate as you climb, so if you fall, they're back. you can probably stay on one level and keep killing them until you have enough points for credit.

ruins rampage: yeah, not good at this one either. just remember that your figure will keep moving until you tap the arrow key again. so little guy's moving up, you tap left, it starts going left. tap left again and it'll stop. i just wandered around and found enough coins to get enough points for credit. if you can run into the urn/vase looking thingies, they'll up your health - so you can survive wandering into the path of more arrows.

whack a ghost: my only hope here was that i got enough points in the first levels, before the keys moved around, to get credit. make sure it's set up to use the 10 key and not the 1 through 0 over the letters.

hope this helps! good luck.