In the circumstances you've outlined, I would stick with what you know and are familar with (ie don't use IR for the 1st time for this! My main reason for asking colour or B&W was you can get slow emulsions in B&W (25asa and slower, wack on red filter, polerizer... instant real slow film ) but I don't know what's available in colour. Also, in colour you're going to have colour casts probably (although that may add to the effect) Either way a ND filter will still be required. Whatever you decided, a practice run (or 2) is definetly in order!
Just for your future knowledge, there's a few IR films available (Ilford SFX, Konica, Maco and Kodak) They all have different characteristics and a few things you must be careful with (Kodak needs to be loaded/unloaded in the dark) but otherwise they pretty much are like a normal B&W film (you need a filter too) There's also a E6 colour IR Slide film (Kodak). Don't know much about that, only used a couple of rolls 20 years ago!!