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Won't immediately help: Amex AU's (ACM's) look like a brand new tradeline; however, it may help later, as it does establish your membership date with Amex and if in future years you get your own Amex, it will reflect the year you were added as an AU in the open date which offsets sometimes completely the negative effects of new tradelines, and can even be a positive in some cases if it was long enough ago compared to the rest of your report.
Also, AU's are funny animals under the modern FICO algorithms (which not everyone is using yet, see mortgages) so it may or may not be counted as far as your utilization goes and might be disregarded altogether if it falls under their anti-abuse algorithm. I wouldn't worry about it though personally, if that's the case won't be the usual new account penalty so we're talking some upside for no real downside: not as good as your own Amex, but ostensibly better than not having one at all for some purposes.
Anyway, what are you still doing with that Credit One card? 
Too many fees for no real benefit compared to your other cards.
Ah sorry, I edited my message, see above . Might help might not.
In reality, with your listed cards we're not talking major utilization changes: the Cap 1 secured is OK cept that it's not useful, the Credit One though has something like 4x the fees of a Cap 1 secured, and that should be on the chopping block first.
Lot depends on what your utilization is, least on these forums you'll normally get advice (good advice at that) to pay down everything that isn't on a 0% promotion offer of some sort but leave a small balance on a card for FICO purposes.
@Anonymous wrote:I didn't want to take a dip in my score by cancelling two accounts at once. I don't keep any substantial balances on my cards. I just use them all month and pay them off. I don't use the Capitol One Secured or Credit One at all any more.
I guess i'll just wait and see what happens after a few months of being an AU on her card and then probably cancel the two lower end cards I have.
I think the only potential dip could be for utilization purposes. even if you cancel those cards today they still will remain on your credit report for another ten years i believe. Rev is correct about 08 scoring in particular , not caring about AU accounts. From personal experience I thought my Amex TE, which is an au/acm account, would show utilization. It was the only one of my cards that was showing an balance. I got dinged for 25+ points on eq 08 for showing no util.
I added my son to my Blue Sky last year and he had absolutely NO credit established (reports wouldn't even pull up his name). Since adding him, he established a credit report (and I also started adding my other cards as I got them) and today he was able to get his very own AMEX Blue Cash and a Discover It. Now the good news is, he'll be able to back date his new Amex to the date I first got mine.
@Juss11 wrote:Was your son already backdated with his AU card on your account? I wanted to have my 20yr old daughter backdated, to when I got mine. But mine is 1987 when i was an AU on my dads account. Dont think Amex would buy that! Also its harder to get AU accounts backdated now.
He just got approved for his Amex today. 