Here are some places worth seeing Bintan..
My favourite is to stay at the Hotel laut Jaya in Tj Pinang Harbour. The hotel is nothing much - but clean comfortable. Go visit Penyenget Island - it is right in front of Tj Pinang. You can spend the best part of day exploring the old fort and palace ruins.
Take a small boat across the harbour to Sengarang and spend a few hours walking around the Chinese temple and Kampung Bugis.
Take a motbike or txi to the hilltop behind the town and walk through the lovely old Dutch houses. back downhill to the main town.
At night, just hang out on the deck under the hotel and eat some seafood and drink cold beer.
If you are staying at the Bintan Lagoon Hotel, try doing their afternoon "African Queen River Trip". It is well worth the effort. I once stumbled on this trip on the web, but can't remember where.
Dont say there is nothing to do in Bintan. I havent even mentioned the beautiful islands of Numbing, Pangkil and Terkulai.