This is from BAA's website:-
Bag content ? Families/babies
Am I allowed to take a baby-bag as well as my own cabin bag, if my child is sitting on my lap?
Yes, even though the baby does not have its own seat, it has its own bag allowance. But do check other restrictions with your airline.
Am I allowed to take my child?s pushchair to the gate?
Yes, you are allowed to take pushchairs, prams and buggies to gate. These items will need to be x-rayed, though, and so your child/children will have to be lifted out at security. The security officers may make further checks of the pushchair.
Am I allowed to take children?s puzzle books, games and stickers on board?
Yes, you are allowed to carry these in your hand luggage through security and you can also buy them in the departure lounge.
Can I take wet wipes on the plane?
Yes, you can carry wet wipes.
Can I take milk powder with me to make up a bottle of milk on the plane?
Yes, you can carry milk powder.
What about a bottle of prepared milk does it need to be a maximum of 100ml?
No, nor does it have to fit in the re-sealable bag. However, the amount must be sufficient for your trip only. You may be asked to taste baby milk and food by a security officer. There are no limits on powder formula and water is available in shops after security and airlines can provide water during the flight.
Can you buy cartons of formula milk from the shops after security?
Yes. Boots sell Cow & Gate ready to drink formula in both 250ml and 500ml after security at Heathrow, Gatwick and Stansted. Every country which is implementing the new security arrangements has accepted that parents with babies should be able to carry sufficient baby food/milk for the journey, so 'reasonable amounts' are exempted although you may be asked to taste them.
What happens if the baby can only tolerate non- dairy and needs Soya or rice milk?
As long as the milk is in a bottle and tasted by the accompanying adult at security that?s fine.
What about jars of baby food?
Any jars of baby food will be required to be opened and tasted, they do not need to go into the re-sealable bag.
What about pureed food in plastic pots or containers?
Any pots of baby food will be required to be opened and tasted; they do not need to go into the re-sealable bag.
Can we take baby car seats (for use on the plane) through security?
Yes and they do not count as your single bag.
Can we carry sandwiches and crisps for the children?
Yes, crisps are fine and sandwiches with any type of filling are also permitted.
Can we carry children?s liquid ibuprofen and paracetamol in our hand luggage?
Yes, sufficient for the trip. You may need to test the liquid medicine by tasting it in front of security.