Adding accounts to a campaign

Hi all, I'd like to know how to add accounts (and all associated contacts within that account to a campaign. One of my colleagues added an identical task to a list of accounts in Salesforce. Some of which have contacts assigned, some of which don't. Therefore I can't do a batch campaign with smart list 'Activity was logged' with constraint 'is task = true' as this only recognises the leads, not the accounts.

The only factor we can distinguish on is the activity/task logged against the account. Is there a way via either SFDC or Marketo that I can search on this and move all accounts into a SFDC campaign?

Thanks!

Jess