If it has a motor, electric or gas, it has to be registered. Also search the forums for methods used to display your registration numbers. There are a lot of ways, but it will help you for when you get on the water, that you'll be prepared.
About being prepared is what I like. You are correct about minimum equipment and lights. However, unless you have a tether, or your fins float, I would suggest at least a collapsible oar. In addition to the whistle, I would pack a small air horn.
On horsetooth, some of the boats are blaring their music so loud that they wouldn't be able to hear a whistle for coming too close (within 50'), but the air horn would get their attention. Also, if you swallow water... blowing a whistle is a bit moot.
So please consider looking into the alternative lightweight, small, devices that are possible to help you stay safe (reflectors on the back side of the toon for dusk fishing, etc).
Be safe guys, pleasure boaters don't always know/follow the rules.