The Casuarina Sands Reserve is a really great place to swim in freshwater then have a bbq, and undercover picnic tables, then use the public toilets. This picnic area is located on the banks of the mighty Murrumbidgee River.
The Hughie Edwards VC Rest Area has a public drop toilet, some picnic tables with some rubbish bins and is quite noisy due to the main road running past. However it's a handy place to stop and have a rest from driving to Canberra.
Molonglo Gorge Reserve Rest Area has a public toilet, plus bbq and a small children's playground, and the Molonglo River is very close if you want to try your hand at fishing, or take a few photos to remember this place.
You can catch some trout at the Paddys River Rest Area, it's a nice place to spend a few minutes, or for an overnight stop if needed. There is a children's playground, and bbqs here.