NParks make a clear distinction between parks and nature reserves. The Lower Pierce Reservoir Park is within the Central Catchement Nature Reserve and thus, dogs and pets are technically not allowed.
http://www.nparks.gov.sg/nparks_cms/dis ... subcatid=1
But... I have been there so many times, and dogs on leashes are not uncommon. The dogs seem to get really excited with the abundant monkeys. I suspect if things don't get out of hand, dogs will be tolerated.
Cycling there isn't much fun, since it's not as developed as other man made parks. There's a causeway leading to SICC, but that's about it.
The most exiciting thing to do there for families is "kelong fishing". Bring pails, bread, and lots of small fish tank nets, stand on the granite rock beach, and try to net small fishes among the rocks. Hours of free fun! Unfortunately, wild fish from reserviors don't do well in fish tanks, so, unless u have a pond at home, release them back into the reservoir at the end of the day. Fresh water crabs and prawns are plentiful too!