Google nonprofit domain switch help

For a school - we have been using one domain name with google for education/nonprofits for many years @reallylongschoolname.org and we recently purchased a shorter domain name @rlsn.org and I need help to either change the domain, create aliases to make shorter email addresses, or perhaps another solution. We use google drive etc in the older domain name and don't want to lose any work or emails. Need someone who can help me choose the best solution and implement it. Needs to be someone familiar with rules for google nonprofit/education and how to make this transition without any interruption.