There are loads of water-facing parklands on the quieter Balmain side of Pyrmont, featuring picnic tables, free BBQs, playgrounds & walking tracks.
It's usually pretty quiet, with only a handful of people to be seen at any given time. There's a large oval too if you're keen to play a game of touch footy or soccer with your group.
It's a good idea to bring along a bottle of water & sharp scraper if you're planning on using a BBQ, as they are stainless steel and difficult to clean. There isn't any public transport that goes directly here, however it's about a 5-10 minute walk from the fish markets light rail station.
Waterfront park is an off-leash dog park as listed by sydney council so this is a dog friendly place. Waterfront park pyrmont is one of the few dog friendly barbecue places in sydney.