@Smart Brit
Thanks for all your input thus far.
Perhaps you misunderstood, only if I fly another airline - other then BA - first class would I not fly first class the way back - as I would have to buy 2 first class tickets for my daughters. However, if I do somehow manage to get availability on BA for first class, I will of course fly first class both ways - as they will not require me to get 2 extra seats for my daughters (as mentioned previously, they turn 2 during the trip). Is there any hope?