Yeah, me and my younger bro went to stay at the Lub D backpacker joint in Silom back in January. The backstreets around this hotel have interesting bars but that's it. Patpong district next to it is the craziest place I have ever been to (and I've been and seen some shit in my life)
We also took advantage during that same January week of the cheap prices for all hotels due to Bangkok still recovering from the October 2011 floods, and stayed in the Grande Sukhumvit Sofitel at Soi 10 in Sukhumvit, the high class entertainment district east of the old city. It's accessible from Nana Station, and will be less crowded during the Songkran Water Festival (which is also on the date of April 11-14 you mentioned in your planned travel dates) - that date which I am also planning to travel with Canadian and Malaysian friends.
Three things I can definitely tell you:
1) The scooter cabs/tuk tuks should NOT charge per person. There is no such thing.
2) Do go over to the Tawan Bar on Soi Tarntawan near Surawong Road (just ask the taxi driver or scooter cab person to go to "Thanon Surawong"). Holy shit the muscle on the male performers will change you forever, I swear.
3) Do keep a lot of change with you if you want to use the BTS Skytrain. Most machines will run out of the ability to change notes into coins during peak hours.