If you log into Google Analytics (via account A), you can set the other account (account B) up as an administrator. You will then be able to access both Analytics and AdWords via Account B. Doing this via Google Analytics is rather easy and I am set up on multiple clients Analytics accounts as an administrator this way. 

AdWords is a little different. Deleting the unused AdWords account is an option but likely not necessary. I often recommend to my clients to keep the secondary AdWords account and use it as a paid account for running display ads which can be highly effective for NPOs. 

If the email account you want to use for everything is "locked" to the unused AdWords account, you can set up a third account (account C) and set that account up as an administrator on your AdWords account, then as Account C, go in to AdWords go to "My Account" tab, then "Access" and then terminate access of Account B.

There can be several nuances to all this so it can be better to walk through it on the phone. Feel free to reach out to me via my profile and we can schedule a call. 

All the best,

Robert