This gentle hike is described in "109 Walks", but the edition we had is out of date with regards the trails here. Check out the webpage for Brandywine Falls Provincial Park for a more recent map, though it's still not 100% accurate.
Referring to that map, we followed the Hydro Right of Way Trail north to McGuire, where you're dumped out onto a dirt road. Follow this to the right and you'll soon see a sign for the trail continuing to the right again. It curves around the boundary of McGuire before crossing the railway tracks. From here, turn left to go to the suspension bridge over Callaghan Creek (which leads to the CalCheak Forest Rec site) near the confluence of Callaghan with the Cheakamus River: hence Cal-Cheak. We re-traced our steps to the railway again and now followed the trail south, initially parallel to the tracks, but then winding your way through open pine forest and passing a few small lakes. This part of the trail is marked "Under construction" on the map, and it soon joins up with the Sea to Sky Trail which you follow all the way back to the parking lot via the falls overlook. My guesstimate is a round trip of about 8 km with about 50 m or so of elevation gain.
With the trail description out of the way, I have to say I quite enjoyed this loop and it should be on everyone's "Easy" list. The mix of open pine forest (very fragrant in the sunshine), occasional ponds and volcanic rocks was really enjoyable to hike through. The suspension is cool and the Cal-Cheak confluence really shows up the difference between the two bodies of water: the Cheakamus River is laden with rock flour while Callaghan Creek is clear. Plus of course you get the impressive Brandywine Falls to admire at the end.
The one thing to be aware of is that the entire trail is multi-use and you may encounter mountain bikers at any point along it. We were lucky and only saw a few on one of the harder-to-bike sections so they were travelling slowly.
Flower report: bunchberry was out near the suspension bridge, Queen's Cup is budding (a few were out already), saxifrage, penstemon and other low plants were flowering among the pines. We found a really nice group of coralroot among a patch of cedars.