|I'm old enough to have grandkids myself, as are many of the helpers in these forums.|
Whoever told you to look for a 128-bit card that supports DX9 gave you good advice. The card I recommended is only 64-bit, but based on the games you listed, you probably don't need anything more powerful. I can recommend a few others but 1st let me give some quick background....
64-bit or 128-bit is the width of the memory path. Generally speaking, the wider the path, the more data that can travel over it during a given amount of time. However, if you use a smaller path & speed up the data, the outcome will be the same. For example, 64-bit @ 400MHz is the same as 128-bit @ 200MHz. It's simple math: 64 x 400 = 128 x 200. What I'm getting at is, all 64-bit cards aren't necessarily bad & all 128-bit cards aren't necessarily good.
The next issue is power. The AGP slot can only supply a set amount of wattage to a video card. I believe it's 42W max. Most gaming cards require more power than that so it has to be supplemented by a direct connection from the power supply to the card. Unfortunately, eMachines are notorious for using cheap Bestec power supplies that have a higher than average failure rate, so adding a video card that requires the additional power plug-in is not a good idea unless you intend to upgrade the power supply as well. Assuming you don't wanna go that route, here's some cards for you to consider:
AGP cards under $50