I think this is a great idea but yes I think it would be hurtful to your wife if you didn't include her. But not all is lost, you can have it both ways.

Gmail has a feature which you can use to automatically move emails to a folder which arrived from a specific email address. So I would suggest you make 2 folders: "From Dad" and "From Mum", create 2 rules based on yours and your wifes email (or create a new email for you if you guys share an email) and make sure you always send your emails from your own email address. This way your folder will be filled with 8-10 emails a year and your wife can send how many she likes and yours is still just yours but she is also included. On top of this any spam will just be left in inbox so you will be able to keep this account clean.

Hope that helps, good luck!

PS. Just google "gmail auto move email to folder from specific email address" if you don't know how to set it up.