application load balancer schedule changes/maintenance page

Hey Everyone who reads,

I'm looking for alternative suggestions. With Covid19 we are cost cutting at work temporarily on some of our on demand servers and have several instances that will be shutdown for few hours each night $$. A colleague is triggering this externally already via our Skeddly account.

During this outage we wish to display a simple html maintenance page.
I have something working in place but believe if i could easily schedule changes to our application load balancer and switch to a static 503 html text (set in the ALB rule) where an existing target group would be could be simpler than what I'm currently doing.
Could changes be schedule with autoscaling, Cloudformation, Lambda/DynamoDB?
(I understand the 503 response is far better for Google and SEO)

My current workaround will help in future for other planned maintenance as it set and forget, I'm just curious what other options you come up with.

I've used Route53 with routing failover routing policy triggered by a health check.
Primary DNS is an alias of ALB
Secondary is either
1 - An S3 bucket DNS Alias http only with a static html file
2 - A Cloudfront DNS Alias that points to the S3 bucket (where we need https as well as http)

What ya got? Thanks in Advance