Another big and not hugely child-friendly airport. Terminal 5 is largely British Airways. There is a family check-in desk, although its queue can be longer than the regular desks, and oversized baggage is nearby. There is no family security lane. Milk, water and pouches are checked separately; buggies need to be emptied but not folded.
There is a Boots for baby essentials and the usual airport restaurants. A very good play area near gate A3 has separate soft-play spaces for under-twos and older children. There are plenty of changing rooms, although those I visited lacked breastfeeding chairs or child-sized toilets and sinks.
Aircraft are usually reached by a step-free air bridge. If leaving a buggy at the aircraft door, watch for the drop-off point before the aircraft. With the correct orange tag, it can be collected shortly after disembarking.
Family passport control on arrival can be long and there is limited seating by baggage reclaim. Heathrow Express, the Piccadilly line and Elizabeth line provide public-transport options; the Elizabeth line should be fully step free.