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.
EDIT:
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 sub.mydomain.com
or www.mydomain.com
then you can use simple CNAME records for everything.