Blake Lively is soaking up all summer has to offer ... taking her kiddos and some friends to Canada for a boat day ... and only TMZ has video.

We obtained footage showing the actress pulling up to the Port Sanfield Marina in Ontario last Friday with a boat full of friends and children, including some of her own.

Blake -- dressed in a red bikini top -- looks confident pulling up to the dock ... where staff members await her. No Ryan Reynolds sighting for this boat excursion -- Blake's the captain now.

Folks who were there tell TMZ ... the group walked up to the store, and her kids openly chatted with some other children who were around.

Blake's been having quite the active summer -- she shared photos from Wrexham AFC's match against Liverpool FC at Yankee Stadium earlier this month, where she was all smiles with her hubby. And in July, the lovebirds were spotted grabbing a rooftop Mexican lunch in Canada.

Of course, they missed out on the summer's hottest event -- former BFF Taylor Swift's wedding ... but it appears they're faring just fine without the superstar in their corner.

Full steam ahead!!!