First, are they long enough to be worn full length? If so, do you have a light coloured hi-top sneaker (for super casual) or a relatively flat heeled bootie? The reason I mention hi-tops is that if it's evening on the lake in June, there will be bugs. And if your ankles are bare, you will get bitten. Also, full length pants plus a higher vamped shoe/ bootie will provide greater warmth. If that won't do, and you want to wear sandals, you will probably need a big of bug repellant. Unless there is a completely screen porch.
I would look at some of Sveta's outfits with her blush pants in the same style. Her thread from this week included one such outfit. You can dress these up a bit with a silky top (if dressing up a bit is wanted) and add a blazer. Another option would be some fluid knitwear. It will be cool enough for that, so might as well enjoy it!