Welcome to the boards!!!
The Poker Run day will not scare anyone, infact, you will be there on a special day. Not everyday that you can see boats running 140++.
The water will get a little rough around the start, at Thompson Bay, but the majority of the lake will be fine. The further down you go, the better. There are plenty of protected coves, where you can have beach activities and wouldn't even know boat were racing by at high speed. Except you'll hear em'!!! You'll have a great time.
RTJas