Here's how I will proceed (divided into 3 phases)
A. Make it work with minimum system requirements
1. Create the basic AWS infrastructure
2. Setup application and migrate the database (for temporary use)
3. Make sure everything is running as expected
B. Make it production-ready
1. Add EC2 instances with Autoscaling & failover
2. Add Database (Multi-Availability zone for failover) with/without sharding/replication if required
3. Make sure everything is running as expected
C. Shift DNS (with Zero Downtime)
1. Setup AWS Migration Hub to sync database changes that might occur during DNS change.
2. Change DNS
3. Validate everything is running as expected, if not then revert DNS and have the Database data sync from AWS (if any updates)
To start, I'll need to discuss some specifics about your Wordpress setup.
Because hosting any application in AWS has some catch which the application itself MUST adhere to prevent any data loss.
Cheers
JAY