I intend to have a few sherberts for sure. Luckily BA allowed us to pre book seats for free so we have the bulk heads with the space for the sky cot so I'm hoping she sleeps most of the way. The slightly hyper active 6 year old we have though, that's gonna be tough to keep her entertained for the flight.
Also, might as well ask here, any restrictions on milk going through security? I worked in the game some years back at Heathrow when liquids over 100ml were banned, but can't remember the policy on bottled breast milk.
It looks like you'll be fine to bring a larger quantity as long as you declare everything to the security agent.
Here's a TSA link: http://www.tsa.gov/traveler-information/3-1-1-liquids-rule