[QUOTE=CheVive;7392884]As I'm leaving from BOS, I might end up taking the sleeper service flight and was wondering if I can have my pre-flight dinner in the First lounge, or if I need to use the Terraces for pre-flight dining./QUOTE]

Terraces for pre-flight dining if you're travelling J, even if you're Gold. Pre-flight dining is based on travel class not BA status.

Which brings us back to a question asked before but not I think answered - is this the only time you'd turn down an at-gate op-up from WT+ to J, given that you won't have been entitled to eat in the lounge and you won't get much onboard?