I have a Macbook 2.0 Ghz Core 2 Duo, 2 GB RAM, and a GMA 950 (much worse than what you got). I can run on medium-low settings very smoothly, on my external 24" monitor at 1920x1200 resolution (resolution seems to not affect AoE3 performance much). Of course, the entire issue is cooling. If you have appropriate cooling, you can run it at whatever specs you want. Our 20" Intel iMac is constantly slowing and crashing during multiplayer games due to heat issues. We often have to turn down its specs, even though it is much more powerful with a not half-bad dedicated GPU, due to the heat.
As for what I do when I play AoE3. I have my Macbook elevated 3 inches, and a small fan behind constantly pumping the hot air out of under it, which gives a big boost. I have
Coolbook installed, which, when properly undervolted (READ: this does not mean
underclocked, and is completely riskfree and negativefree) lowers my AoE3 temps by 20-30 F. I have
Fancontrol installed. And playing with an external monitor (and keyboard) seems to lower the temps by 5 F or so.
The point is, your specs are not as important as your cooling. I have every graphics option available to me (which is fairly limited on my system) enabled, and run AoE3 at around
145 F during an intense multiplayer LAN game. Before I had all of these cooling options options in use, my machine ran AOE3 at
185+ F. If you take the effort to cool your machine (definitely not playing on your lap), then your better integrated card will handle it excellently.