Lisbon is a wonderful city with children and it has one genuine obstacle: it is built on seven steep hills paved with calçada, small polished limestone blocks that are slippery when wet and hostile to wheels.
The hills, practically
Alfama and Bairro Alto — the most atmospheric neighbourhoods — are steep, cobbled and full of steps. A pushchair there is hard work.
A carrier is easier for younger children. For older ones, the hills are fine and the funiculars are fun.
The funiculars and Elevador de Santa Justa are public transport, covered by a transport card, and children generally enjoy them.
Base in Baixa, the flat grid between the hills, or in Parque das Nações, which is modern, flat and spacious.
What works
The Oceanário at Parque das Nações — one of Europe's largest aquariums, built around a single vast central tank you circle on two levels. Reliably the highlight for most children.
The surrounding area is flat and modern with a cable car along the waterfront, open space and the Pavilhão do Conhecimento science museum next door.
Belém — flat, on the river, with the Coach Museum (gilded carriages, better with children than it sounds), the monastery, the tower, wide-open riverside space, and the original pastéis de Belém.
Tram 15 to Belém is a modern tram with room for a pushchair, unlike the packed heritage 28.
The castle, São Jorge — walls to walk, peacocks, and a view. Steep approach; take a tuk-tuk or the 737 bus up and walk down.
The beaches — Carcavelos and Cascais on the train line west, half an hour from Cais do Sodré.
Sintra with children
Pena Palace works — brightly coloured, on a peak, and looks like a fairy tale.
Quinta da Regaleira works better for older children, with its initiation wells, tunnels and grottoes.
The difficulty is logistics: steep walks, queues, crowded buses. Go early, buy timed tickets in advance, and pick two sites rather than four.
Eating
Portugal is straightforwardly child-friendly. Restaurants welcome children, and the food — grilled fish, chicken, rice, soup — is uncontroversial.
Frango piri-piri can be ordered mild. Caldo verde, the potato and kale soup, is a reliable option.
Meal times are less extreme than in Spain — dinner from 7:30 or 8pm.
The couvert, brought unasked, is charged. Refusing it is normal.
Practicalities
Tram 28 is a pickpocketing hotspot and packed. With children, take the 12 or a taxi.
Viva Viagem card for metro, trams, funiculars and buses. Children under a certain age travel free — check the current threshold.
Summer is hot and the miradouros have little shade. Spring and autumn are considerably easier with young children.
Apartments with a kitchen and a washing machine are widely available and usually better value than hotel family rooms.