There is a path at the end of Lake Thomas Crescent. It starts on the edge of the gravel driveway at the end of the road, it may be difficult to find your first time. Once you find the path, it is quite rugged and technical but it is fairly short and mostly bikable.
Once you are thru the path, you will come out next to the highway and the lake. There is a bridge that will take you under the highway and put you on a gravel path. You will now be in MacDonald Park.