I can't say for sure but I don't think he will see anything until an actual financial transaction is conducted. As long as you cancel at least 24 hours before the trial ends, or you have sufficient personal account balance to pay for any subscription then no record of your purchase should be transmitted. However, you may need to take additional steps:
Click on this link to learn how to 'Hide purchases from the App Store '- Hide purchases from the App Store - Apple Support
- "When you hide an app, it won't appear in your list of purchases in the App Store. If you use Family Sharing, the app also won't appear in family members' purchases and won't be available for family members to redownload. But the app will still appear in your purchase history."
- "Hiding an app doesn't cancel a subscription. If you use Family Sharing and you hide an app that you subscribed to, the Family Organizer will still be notified of charges each time the subscription renews." Again, I think this only happens if the Organizer's card is actually charged, not if you pay for it yourself.