Mothers Belinda Robinson, Johanne Beirne and Julie Hunn often take their toddlers to the purpose-built playground and say their littlies love the beach, signposted as a children's beach, where they will peel off their clothes for a swim or paddle.

Ms Beirne's five-year-old son boasts of the experience. ''He says he has been swimming in the ocean. In the absence of an ocean, this is the next best thing,'' she said.

Under shady gums the land is at the centre of debate over a proposed slipway, where boats can be pulled from the water, inspected underneath, repaired and have their motors stripped down.

The ACT Land Development Agency wants the slipway at the peninsula instead of its original location at Kingston Harbour, which is flanked by luxurious apartments with sweeping lake views.

The Walter Burley Griffin Society objects to the development, which is now being assessed by the National Capital Authority. The society, which promotes the planning legacy of Canberra's first architect, says the peninsula should be kept as open parkland, as Griffin had intended.

Building a slipway, heavy winch and workshops would involve removing 18 trees, including 12 big river oaks, and planting pin oaks and crepe myrtles.

Land Development Agency chief executive David Dawes said the slipway's main purpose was inspections of the lake's commercial vessels to ensure they complied with safety requirements. Generally, these inspections take place annually in winter.

Ms Robinson takes her two daughters to the peninsula in warmer months to feed the swans and play on playground equipment.

''I'm concerned the kids won't be able to roam around as much, with the extra vehicle traffic and boats, that will add to the noise,'' she said.

Ms Hunn's three-year-old son and five-year-old daughter like the sand and play equipment. She said the peninsula was an interesting, surprising choice, given its proximity to the playground and beach.

The ACT Economic Development Directorate said the proposed slipway would be 300 metres from the children’s beach area.