At EWR you'll use the BA Lounge. If you are carry on luggage only you may be able to do mobile app check in (depending probably on your citizenship situation) and avoid the check in counter. In the lounge you can ask at attendant at the buffet for Champagne and they'll get you a glass if so inclined. Avoid sitting at the window in the lounge as the ventilation system is set on hyper blast.

The second meal on board I was told is on a schedule (approximately 8 hours after the conclusion of the 1st meal) and can't be done at a time of your choosing. That said, I missed the second meal by sleeping on the return (to JFK) but since I ordered book the cook, they hadn't cooked the meal - so it was still available to me ~12-13 hours after departure.

All and all, the nonstop, although a long flight, is a very pleasant way to make your way to Singapore.