See our round-ups of the best child car seats, baby slings and pushchairs1. If you're travelling with a child under 18 and your surname is different to theirs, you'll need to carry documentation to prove your relationship with them or the reason you're travelling. Make sure you check our list of Don't Buy child car seats beforehand to avoid getting stuck with a seat we don't recommend. You can take enough baby food, baby milk and sterilised water in your hand luggage for the journey, even if they exceed the usual liquids limits, as long as you're travelling with your baby. You can take enough baby food, baby milk and sterilised water in your hand luggage for the journey, even if they exceed the usual liquids limits, as long as you're travelling with your baby.