Tikal is an hour and a half from Flores and almost everyone goes with somebody, because the shuttle, the park fee and a guide are easier bought together than separately. This operator runs the standard day, the sunrise trip that gets you inside the gate before the howlers start, and the sunset one, which is quieter and has better light on Temple IV.
They also run the harder-to-reach Petén sites — Yaxhá on its lakes, Uaxactún, and the multi-day walk in to El Mirador, which is five days on foot through the forest and not to be undertaken casually.