People disagree about Slime. I use it on my Mountain bike, and never get punctures, others say it just clogs the valves up. It adds weight, but not much. A 16" wheel won't take a lot - do leave room for the air.
16" wheels are fitted to Bromptons and other bikes, and punctures are less frequent than we might think. They're a nuisance when they do happen though. Max pressures are your friend, in my pneumatic opinion.