As soon as an item appears the kids seem to run and hide.

Hide? There is nowhere for them to go.

they are all around as soon as an item appears they run all over and arent in the places they were before

Generally, you can always find one or two around the bathroom area, several trying to reach the coconuts and a few checking out the flower north of the research table. A few love to sit south of the fire and they all love playing tag.

Plus, there's often one or more feeling lonely, so they'll go and sit up in the top left-hand corner or down at the bottom, next to the mosaic.

If youre children seem elusive, I find pausing with the spacebar very helpful. You see an item, and BAM! It won't disappear while you go grab a kid :).

Hum! I pretty sure that the item will disapear in a few time! The time for the collectibles and mushrooms is not related with game time, they appear and disapear independently.

Laurence is right pressing the space bar doesnot do much for collectables dissapearing or staying very long. The reason for this is that they stil regenerate even though the game is on pause.

Bacically the only benefit of pausing while getting a collectable is the children are easier to "find" or pick out of a crowd because they are paused.

I have noticed my items disappearing anyway, but I thought it was because it was already about to disappear.

Because the kids usually run everywhere, it is often easier to find one without using the spacebar as their movement can be seen, so they stand out from the rest (apart from runners, of course).