Alas not. The 7-day trial is a full trial, so if these Sky channels do not appear in NowTV for you, they will not be there on a subscription either.
If you want these channels, best stay with Sky, or seek elsewhere for them, and don’t forget to cancel your Free Trial well before the week is up, so you won’t move on to subscription, and get charged.
The Free Trial will still last the whole week; Cancellation just ensures it won’t continue, chargeably, afterwards.
Set a Payment PIN on your account so that no-one but you can buy memberships on it. Check your bank accounts monthly for any other unexpected payments to Now. That way you can at least nip them in the bud, while you and Now figure out whose fault they are.