Well then, I've been instructed to call everyone, so please come along.

Literal

Well-then, everyone [also-も] call-come [purpose-ように] been-instructed-[resultative-てあります][reason-ので] please-accompany-[polite-くださいませ].

言いつかってあります 'I have been instructed' — 言いつかる 'to be ordered' + てある (resultative: the instruction still holds). ご同道くださいませ 'please accompany me' uses ご同道 (honorific + 'going together') + くださいませ (very polite request form). The language is old-fashioned and highly refined — servant or retainer speech.