It sounds informally OK to me. It's clear that the invitations ('invites' itself makes the sentence informal) are individually written and 'tailored' to each guest.
Here's just one of the dictionaries that confirms that 'bespoke' is in use in the modern world in relation to websites and computer software; it's not limited to clothing.
(You mention 'my dictionary'. Have you bookmarked the OneLook Dictionary Search?)
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