DateTime as an option in an ion-select

I’m needing to have 3 options in this select, one being “ASAP”, the other being “Urgent” and the other allowing the user to select a custom date. The method I’ve tried just renders a blank option as the third one. Any help would be greatly appreciated.

Below is my attempt:

<ion-select formControlName="requiredBy" cancelText="Cancel" okText="OK">
    <ion-option value="asap" selected="true">ASAP</ion-option>
    <ion-option value="urgent">Urgent</ion-option>          
    <ion-option value="date">
        <ion-datetime displayFormat="DD MMM YYYY"></ion-datetime>    

Hi! How did you manage to do it in the end?