I'm not an expert but a big thumbs up for lots of seaweed and tofu.

keep to the Fen Causeway

Oriental Restaurants: Chinese, Japanese, Thai, Vietnamese, & etc. normally have vegetarian options to attract Buddhist patrons.  Indian restaurants also but they are more expensive, at least here in the states.  Mexican restaurants will usually sell a bean burrito platter with the burrito made with vegetable shortening instead of lard -- have to ask.  Various Levant and North African dishes are vegetarian ditto for sub-Saharan African.  Some forms of Jamaican Pepper Pot (Callaloo)  are completely veggie; be prepared to have the top of your head blown off.  ;-)

One thing we've done when going to a restaurant with a large group is to  purchase, in advance, a vegetarian option for them who want one.  We've always told the chef to make what he/she wants, subject to a price limit.  Chefs here in the US get really tired of cranking out 'The Same Old Things' off the menu and enjoy the challenge and creativity of doing something one-off, as it were.  Sitting down at 'off-times' helps clinch the deal.

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre