a friend bought our dd a little bag with four chicks in at easter and she loves me to hide them round the house then go and find them - i have to give her quite obvious clues (btw the credit for thinking up the game goes to my lovely friend not me!) like 'the chick needed to brush her teeth' or 'the chick wanted to read a book'. The great thing is when there are two of them they seem able to play this for ages, hiding the chicks for each other (often in the same places!)
another version on sunny days is to 'hide' a load of those plastic balls you buy by the bagfull around the garden then give them a bag each and get them to gather them up. requires some parent participation but its fairly minimal (no clues required here).
bet those of you with more than one dc have got LOADS like this, fancy sharing? (OK I'll come clean - have dd's friend coming over for a couple of hours this am and its too rainy to go out!!)