You might get some info here...

http://www.puertopollensa.com/

If you mean suitable for two 5-year-olds then I'm sorry I cannot help as my days of looking after kids of that age are long gone.

have a look on http://www.no-frillsexcursions.com for a list of most of the attractions on the island. No frills have several ticket outlets once you are in resort so you don't have to make your mind up before your holiday. You can book either book trips with transport or if you are hiring a car it is still worth booking through them as you should pay the same as the gate price and avoid some queues...
Personal fave's are Pirates show, Caves of Drach, water parks and Rancho Grande...
If you don't want to go for major attractions, then just head off and explore; the scenery and views out of Pollenca towards Cap de Formentor are amazing, and it's nice to look around the old towns of Pollenca and Alcudia although not so much fun for your children...
The Hidropark in Alcudia is convenient and although smaller than the Western water park and Aqualand at the other end of the island, is half the price and great fun for kids...
Enjoy....!