Looked at shard, novelty is view and height but reviews mixed and prices too high for a bad experience.
Looked at suck and waffle and similar... Mixed reviews unpleasant service.
Thinking of boat maybe?
Or rules in Covent garden... Or perhaps a wow cream tea instead in incredible memorable place
Or somewhere with tons of atmosphere. Ideally Greek place smashing or belly dancer would be fun but latest feasibly eat with dc is 8.