Westow house, crystal palace, bridge tavern penge, sylvian post forest hill. All urban shabby chic and chilled, kiddie friendly. Typically around £12. Crown and greyhound dulwich village further out, or florence herne hill.
I'd also add the Exhibition rooms, Crystal Palace, The Albert in Deptford and most Antic pubs are generally very good.
Unfortunately the best ones around Sydenham are now either estate agents or aren't particularly good. The Woodsman's Sunday Roasts were incredible (when it was a pub).
We've been in Sydenham for a few months and trying out local Sunday lunches has been a mission. Agree with some of the suggestions above, especially Westow House in C.P, and Dartmouth Arms in F.H.. Sylvan Post has won on most generous serving - and quirkiness of decor.
We'd also recommend White Hart in C.P. and Dulwich Woodhouse - which is actually on Sydenham Hill. The Woodhouse is in a lovely location - take a walk through the woods to work up an appetite and leave your wellies at the door - but it can get very busy.
Looks like we have a few more to try from the other suggestions!
Oh, yes I forgot about the White Hart, probably the best one we have had locally.
We haven't had a roast (dinner) at the Dolphin for a while, it's never been bad, it's actually been good, it's just a bit dull. I can't put my finger on it. Sometimes you get good service, sometimes you don't, some dishes are good, some are ok. I like the Dolphin, but I want to love it. It just doesn't quite cut the mustard compared to the competition. It's not far off though…
It's a bit far, but if you're in that area anyway - Tafalgar Tavern on the Riverside, in Greenwhich. It can get very busy in the summer, or a warm sunny day, but the roast is very nice, and the view of the river, and Isle of Dogs is superb.