I feel ya
Don't worry about it, friend, it happens to the best of us. I will say that you have a cool story, and I know what it's like to just kind of fall into the hobby and be given wrong advice. At least you didn't have to take the advice of a Wal*mart employee (no offense to anyone who works at wal*mart.
You should be fine with the CAE, even though a lot of people claim they get very aggressive and territorial when they're older. I haven't had this problem with them much at all, and keep them to help maintain my tanks. What I do notice, is if you feed them every day, they can get lazy so be easy with the Algae Wafers, only feed 'em if there's no visible algae.
Anywho, I would say with the Guppy and Molly's, you're set pretty well, get you a few more of them and they'll be happy. Of course, if you just want variety, Platy's go well with them, and like somewhat similar water conditions.
I hear that swordtails are great with them as well, but I've never kept them. A few suggestions:
Corydoras (yeah, they get timid so add one or two more
)
Platy's --livebearer and easy to maintain.
Red Rasboras are beautiful, and if kept in groups of 6-8 are quite peaceful to watch (I personally enjoy shoaling fish along with non-schooling fish, it looks nice.
Flying Fox--not to be confused with Siamese algae Eater. Non-schooling, and enjoys being alone.
Best of luck to you, if you get some male's and females (among guppy's and Molly's), please PLEASE, be sure to have a good ratio of males to females (1 male to 2-3 females) as the male molly or guppy will harass the females for breeding and it can be quite stressful to her. So having more females spreads this out and everyone's happy!
--Sidenote: be prepared to buy another tank to rearing fry if you do that!