Hi good call for a Riverside hotel. The Chatrium Riverside is worthy of consideration. River view suites are large quiet and comfortable, great breakfast. They are currently upgrading the rooms and are working up from the lower floors. If you want to pre book any tours you could try Wandee Wandee@wandeetours.com. You could book tours that include round trip transfers from the port or just do transfers.
Chatrium location is good for getting around, 15 minute walk to Asiatique and hotel has own ferry in opposite direction to Taksin pier about 10 minutes.
Have a great trip whatever you do.