While the above advice is correct for purchasing individual E+ flight access fees, there is one approach worth looking at, especially when purchasing E+ for multiple people for multiple trips ---
E+ annual subscription. The purchase for a annual subscription is eligible PQPs for the purchaser and can cover multiple people. Need to price this out for the travel in a one-year period (a.nd you will need to be one of the travelers)
Economy Plus Subscriptions -- Q&A, issues, ....