If you stay on the market long enough, you should be able to find a 2010+ Ski nautique 200 with an open bow for under $40k. It will definitely only have a 5.7 engine, but for your purposes that will be fine and it will likely have quite a few hours on it. But it is there if you look hard enough and wait around long enough.
If you don't want to look that hard or wait that long, then Malibu had the open bow walk through way back to the early 2000's, so across their models, you should see a nice linear scale of age and hours vs. price. Meaning: for malibu, 40k won't be a "weird pricing point" as @keithh2oskier mentions. You won't have to look as hard and wait as long to find an open bow malibu response right in your price range. And the case could easily be made that it's a boat better suited for open water anyway.
Also, a separate note and some input you didn't ask for - if you are taking larege-ish groups out onto public water, I would highly recommend looking for one with a tower. A tower makes big group public water life SOO much better. But, adding the tower requirement will make it even harder to find a SN200 for under 40k, and will push you even more toward a malibu given that price constraint.
I love Nautique. I own a Nautique. But it sounds to me like the right boat for your situation is a malibu. Something like this boat being a good starting point to begin your research.
https://www.ski-it-again.com/php/skiitagain.php?endless=summer&topic=Search&category=Boat_3Event&postid=53792