I just finished a split stay at Pop Century/All Star Movies. I think you two will have a fine time. It's more important that you're at WDW, not so much which Disney resort you're at. Kids seemed to love the huge icons scattered around the resort. I took the time to look at All Star Music as well as All Star Movies. If you get time, stop over to Movies, especially Toy Story area. The pools were great, however, no slide.
I'm used to staying at POR and this was my first visit to Value resorts. My only comments, and they might not be important to you, are that the All Star resorts did not have espresso machines. I dearly missed this. The Food Courts were small-ish and the menus were the most limited of any I've seen. The gift shops were small and had limited selections.
Pop Century, on the other hand, had a large, expansive Food Court with lots of food choices including flat breads. They had an espresso machine. A short walk across the Generation Gap bridge was the new Art of Animation resort, which had a completely new and different Food Court that I personally loved. The Gift shop at Pop was very comprehensive. Matter of fact, an item I saw there, I later tried to find at every park and DTD, and the shops were out of stock. I had to go back to Pop to get it. Your child will love roaming around Pop and AoA, they are cool and so pretty on either side of Hourglass Lake.
If your great deal covers Pop, for a few dollars more, I would seriously choose Pop Century over All Stars. Just my opinion. Have Fun!