Just some suggestions that I can think of:
1) Watch a movie
- the usual excuse for outings! 
At Bishan Junction 8, Causeway Point
etc.
2) Kopi / Lunch / Dinner
- Junction 8 (Swenson's, Pastamania, Coffee Bean, Olio Dome (Bishan
CC))
- Causeway Point (Seoul Garden, quite a few others - can't remember
off hand)
- AMK Central (S11 kopitiam and others)
- Serangoon Garden - Chomp Chomp; there are also a couple of eating
places ard the interchange, maybe someone who is familiar with the
area could recommend a place
3) Bishan Park - picnic (?), cycling, blading, fishing.
4) Bowling - Kovan, AMK
5) Tennis - Yio Chu Kang
I think some of NEC's previous outings were at Chomp Chomp. Don't
think people would have a problem going there again for food and
kopi.
