This coast was practically designed for children: shallow warm bay water on one side of the peninsula, sandcastle-grade beaches everywhere, seals with an 11am feeding time, a real tall ship to climb through, and enough aquaparks and museums to absorb any rainy front the Baltic sends.
The two structural tips: base yourselves on calm water (Puck Bay side, or the lagoon at Krynica) if your children are small — the open-sea surf is for confident swimmers; and use the trains, which small children treat as an attraction in themselves.
The grey-seal research station is compact, cheap and perfectly pitched: feeding demos, an underwater window, and the beach right outside. Arrive 20 minutes early in summer.
A 1909 tall ship and the WWII destroyer Błyskawica moored side by side — ladders, decks, gun turrets. Pure catnip for the 6–12 bracket.
Children experience the walking dunes as the Sahara. Rent bikes or take the electric carts to the boardwalk, then let them run the bare sand ridge.
Knee-deep, warm, waveless water for hundreds of metres — the safest swimming on the coast, plus beginner windsurf lessons from age 8 or so.
Poland's biggest zoo in a forest valley, then the whispering grotto and palm house in the cathedral park. Combine with the organ's cherub show.
Sopot's aquapark handles ordinary rain; the giant one at Reda (near Puck) with its shark tunnel and wave pools is the full weather-emergency destination.
Drawbridges, portcullises and knight-sized armour — the audio guide has a children's track, and the courtyards absorb any amount of running.
Climbable locomotives at the railway museum, then the open-air village museum with its windmill and lake beach — southern Kashubia's family double-bill.
The tiny summer railway trundles between beach villages — children wave at everything, parents beach-hop without the car seat wrestle.
Give them a jar and the wrack line after an onshore blow. Real finds are small but genuinely common — and the Amber Museum in Gdańsk closes the loop.