If you do visit the Labrador Tunnels, immediately just up the hill behind the tunnel site (along Pepys Road) is a small museum called "Reflections at Bukit Chandu".
The museum is built in the colonial era house where the Malay Regiment did its "last stand" against the Japanese, holding out till they were effectively wiped out.
The museum is also smack in the middle of Kent Ridge Park which follows the ridge line of the hill. Kent Ridge Park features a couple of attractions which may be of interest to you:
(1) They have an AMX-13 on static display in a car park about 200 meters west of the museum. You can get some nice detail shots of the tank in case HobbyBoss releases it later this year (they already have a Panhard with the AMX-13 turret!)
(2) On the nature side, they have a nice (and shaded) "tree-top" walk. Basically it is a walkway built at tree top level (30 feet above the ground) with plaques every few feet describing the trees and flowers. Furthermore, they have a historical map halfway along the walk showing you the locations of various battles in relation to Kent Ridge.
(3) They have a M114 Howitzer a little bit further past the AMX-13 near the driveway into the park.
Unfortunately, my wife got tired of me visiting historical sites around the island so I never got to the Labrador Tunnels. I am saving that for a future trip to Singapore (not sure when though).