Okay, there's no use in wondering whether it's a good deal . . . let's figure this thing out . . . the upgraded card is $30 extra. I'm operating on the assumption that you've already decided to pay the $45 for the regular membership, so I'm ignoring that portion of the cost. Only the $30 is in question.
With the upgraded membership you get a 2% rebate on things you buy at BJs. So . . . every time you spend $100 you get $2 back . . . so you will "break even" once you've spent $1500 (or $125 per month) and you'll get back your $30. After you pass the $1500 mark you start "earning money".
Keep in mind that not everything at BJs counts towards your rebate totals (I took this straight from BJ's website); these items do not count: Food Court, travel, optical, cellular phone services, one-hour photo processing, auto buying, tobacco, alcohol, gasoline, BJs Gift Cards or Gift of Membership Certificates, Membership fees, and prescription drugs. Too bad -- some of those things would've really added up!
Keep in mind, too, that you won't get a check for the 2%. You'll get BJs credit. So you can't use it as a savings account, but you can use it as a grocery account.
Personally, I would not buy because of the promise of "extra coupons and offers". We all know that when we look through a pack of coupons we usually find 2-4 that we want and 25-30 for items that don't interest us. I'd make the decision based upon the numbers and consider any good coupons a bonus.
A good deal for you? You have the numbers now -- you decide based upon your family's needs.