If you’re ready to give away shares in the company, they should be available to be shared equally between all other shareholders (shareholders agreement probably takes care of that anyways)

These shareholder agreements also often have a leaver provision that gives rights to the company or other remaining shareholders to buy back shares from a key executive leaving who had access to equity under preferential terms.

In your case if nothing of the sort is written yet, maybe you can agree with other shareholders a fair value (per share) for the company today and give other shareholders a call option on part of your shares at that strike price. This way you retain full upside on a fair amount of shares and the company / other shareholders have access to further upside on the rest. In one of of my companies we consider this pool of shares quasi treasury stock that can be allocated at a later stage to key executives.