We booked a Sarajevo tunnel tour with Funky Tours at the last minute and were helpfully attached to another group. Funky Tours were prompt with replying to our emails and very helpful.
The tour was about 4 hours long, we were driven to major sites around Sarajevo by a guy called Skender who was about 8 when the siege started and narrated our tour for us. He was excellent - he gave a comprehensive and objective history of the events in the Balkans leading up to the siege that really helped put the pieces together. He gave us a good tour of the tunnel museum in a very tasteful and sensitive way, and then showed us some places higher up in the mountains. For example, we visited one of the locations used by the Serbs to snipe on the famous Sniper Alley that you so often see in news footage of those times.
Skender gave us a lot of detail and perspective that you just can't get by looking at the major historical events - he was there as a child/young teenager and it was a really interesting and really unique kind of tour. Next time we go back to Sarajevo we will definitely do one of his tours again, maybe one to Srebrenica.