From the AWS info page on Elastic Load Balancing:
Traffic to the DNS name provided by the Elastic Load Balancer is automatically distributed across your load balanced, healthy Amazon EC2 instances.
So in essence, Amazon provides you with a DNS name to map your records to. This would be using a CNAME record as opposed to an A record. The DNS name of the load balancer should not change therefore you never have to deal with IPs which as you point out might change.
AWS has always supported direct CNAME links to subdomains and wildcard subdomains for a root domain with simply CNAME records. So essentially it looks something like:
www.mydomain.com -> my-aws-01-elb.aws.amazon.com
Then for your root level domain you have two options, either setup DNS forwarding with your DNS host provider so that
mydomain.com -> www.mydomain.com or utilize Amazon's Route 53 service to host your entire DNS zone and let them manage and setup the required records to get root-level domain support.
If you don't need root domain level support and using a subdomain such as
www.mydomain.com then you can use simple CNAME records for everything.