It is indeed a good hr practice. you have to plan it in order to attain the true picnic pleasure. There must not be any boss/supervisor relationship. firstly decide with all team the spot e.g. either they want to have a 1 day at some historical place then plan activities according to place like historical events if some one can share, the people life style, food habits, music (u can dedicate songs) and others like
menue planner reward
the best guider
the best tour planner
best activity
best joke
best song
some playing activites (chess, bedminton, football)
best photo at picnic
perodies of colleagues
best about a person
bad habit of any one (should rectify it)
Arooj