You are flying tomorrow for a 100 day trip and haven't purchased a ticket yet?
Looks like you can get a $850 one-way fare on UA 89 EWR-PEK and there are tons of Economy Plus seats available which you can get with your silver status, so I think no question go that route. As far as adult beverages, they won't be complementary but honestly you'll be happier with more legroom in E+ so spend your money on a few drinks on board instead.