I thought it might be fun to try orienteering! Basically it is finding somewhat hidden markers in the woods using a map and a compass. This gives one an excuse to do something while enjoying a walk in the woods on a beautiful day. There are courses ranging in difficulty from absurdly easy to "challenging". (I would suggest starting with the former.)
You can go individually or as a group. Instruction will be also provided. GPS's are frowned on but can be used in an emergency!
For more information look at the New England Orienteering Club website at : http://www.newenglandorienteering.org/events-schedule/eventdetail/307/-/neoc-great-brook-farm . Some competitive individuals make a race out of it but that is not necessary to enjoy it!
When you find the NEOC website there will be tons of information. The cost will range from $0 to $10. There is an additional cost to park at Great Brook Farm of $2 - see http://www.mass.gov/eea/agencies/dcr/massparks/region-north/great-brook-farm-state.html for more information about this excellent park.
If you don't have a compass one will be provided!