Going to trip soon, a 4day 3night stay at bali. need some advise.

1) Do i need to get more CF card. I have one 4Gb CF card.
- if getting new CF card do i need to buy more then 1? cause some people might say don't buy big volume card if anything happen to the card all picture gone. Better get two 8GB rather then one 16GB or two 4GB rather then one 8GB.

2) Is Flash is a must ?
- thinking of getting one but not sure if i will need it during the trip.

Please advise. thanks