You can also have a look at https://stacktape.com (full disclosure: I'm a founder). It's a Heroku-like PaaS that deploys to your own AWS account.
We support both serverless and container-based workloads (Fargate and EC2), and many AWS infrastructure (RDS, Aurora, MongoDb, Redis, OpenSearch - ElasticSearch, Bastion servers, etc.).
We're IaC-first but also provide a UI for.
We can do a hans-on assistance with the first deployment, and can also do a custom pricing (as you are a non-profit).
That being said, our deployment engine is pretty powerful (in terms of supported AWS infra resources), and it's based on AWS CloudFormation (with a fallback to making native AWS SDK calls to speed up the deployment, when doing the whole CF deployment procedure is not needed). And we do that in a way so that you don't have to worry about CloudFormation drift, or any unexpected surprises.
You can also configure more advanced things, such as Alarms based on selected metrics, budgets based on AWS (forecasted or actual) spend, and also deployment progress notifications. The notifications about these can be sen to your Slack or MSTeams channel, or to an email.
We also support GitOps flows - push-to-branch-to-deploy or even preview deployments (creating ephemeral, short-lived environment for pull requests, that will get automatically deleted when the PR is closed/merged).