This may be addressed by the Pinpoint FAQ
Q: I already use Amazon SNS or Amazon SES. What do I gain by switching
to Amazon Pinpoint?
In typical Amazon SNS and Amazon SES use cases, you have to set up
your application to manage each message's audience, content, and
delivery schedule. These same features are built in to Amazon
Pinpoint. With Amazon Pinpoint, you can create message templates,
delivery schedules, highly-targeted segments, and full campaigns.
Pinpoint also appears to be able to push notifications to users through the users preferred contact mechanism. This means that you are not limited to SMS and you reach your users with activation codes through the means they want to be reached. It also allows two-way communication.
The Pinpoint homepage also says:
You can send direct messages—such as order confirmations, welcome
messages, and one-time passwords—using the console or the Amazon
Pinpoint REST API. You can also use the API to build custom
applications that deliver campaign and transactional messages across
multiple channels.
This suggest it is suitable for your uses, though it has additional mass-communication features you do not currently need.