It’s best practice to keep the influencer front of mind when developing an influencer campaign, to be sure they can work collaboratively on it. What is the benefit for them, how would their content fit into the strategy, and what value can they bring to the campaign?
The campaign needs to be mutually beneficial for everyone involved, and there needs to be a substantial offering for an influencer from the beginning, so ensure this is developed alongside the campaign strategy. If there is nothing in it for them, then why would they want to be involved? If you wouldn’t do it for free, why would or should they?