As most "kiddie games" go, this one's an easier one. A straight playthrough while finding collectables, then mopping-up by completing challenges. These challenges range from a piece of cake, to a bit tricky.

Overall, you should have yourself a new Platinum in around 5 hours.

If you want that Platinum as quickly as possible, follow one of the crystal location guides under our Links tab, and continue building your crystal set as you work your way from beginning to end of the game. For the Dedicated Collector trophy, you will need 16 crystals for each of the 5 sets. You will find 3 crystals in each level, which won't be enough when you complete the game. However, you can spend fruit on crystals in the store.

There are also a number of challenges to complete, which you can either do once they're unlocked during your playthrough, or after having completed the story. The choice is yours. Many of these are quite easy, and you shouldn't have any problems clearing them on your first try. Though you may encounter the odd challenge that can get pretty tricky. Just keep practicing, and you'll get it.

This is a fantastic Trophy Guide by SwatTJ, which includes videos for the challenges:
http://www.playstationtrophies.org/game/ice-age-3-dawn-of-the-dinosaurs/guide/

And another Trophy Guide here, by Kevinnummer1:
http://ps3trophies.com/forums/showwiki.php?title=PS3-Trophy-Guides:Ice-Age:-Dawn-of-the-Dinosaurs-Trophy-Guide

Here's a Crystal Locations Guide, by ponypo2001:
http://www.xboxachievements.com/forum/showthread.php?t=158111

And a text-based Enemies Guide, by Marcel Martin:
http://www.neoseeker.com/resourcelink.html?rlid=225358&rid=194076

Lastly, here's a basic Trophy List:
http://www.allps3trophies.com/retail-games/ice-age-dawn-of-the-dinosaurs-trophies.html