Sounds like you have it working, that's great. You're welcome to ask for more help as needed. Depending on how young your grandson is it can be quite a tall order to figure out how to do everything needed to get into space. There are good tutorials on the wiki:
http://wiki.micdoodle8.com/wiki/Galacticraft also plenty of videos on YouTube.
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For future reference or anyone else who needs help installing:
* Mods are usually made for older versions of Minecraft than the current/latest, because it takes time after a new Minecraft is released to update mods to work correctly with it
* Most mods have a Minecraft 1.6.4 version; some also have a 1.7.2 version already -
http://www.mmo-champion.com/threads/1210470-Fuzzzie-s-1-7-x-Mod-List; Galacticraft is a couple months behind these because our mod is more complex than most, also we are adding new features
* Your best bet is to stick to Minecraft 1.6.4 mods for the next month or two
* Minecraft 1.6.4 mods need Forge 9.11.1.965. Forge which can be downloaded from here:
http://files.minecraftforge.net/ When installed, it should create a 'Forge' profile in the Minecraft launcher. Choose the 'Forge' profile, and in the 'Edit profile' settings, make sure it is set to use 'release 1.6.4-Forge9.11.1.965' and then press 'Play' as normal.
*If Forge is working ok, mods are installed simply by placing the mod's .jar (or .zip) file in your .minecraft/mods folder.
Galacticraft works great alongside other mods. I recommend NEI (Not Enough Items) which helps the player with recipes and such like. Galacticraft has power systems in the form of a Coal Generator or Solar Panels, but it is also good to accompany it with one of the industrial electrical mods like Mekanism, Thermal Expansion, or IndustrialCraft2: that should speed up the process of refining metal ores and the other items the player will need to create rockets and space bases.
If the install seems too complicated, there are also modpacks like Tekkit and Attack-of-the-B-Team available through the Technic Launcher which do everything for you -
http://www.technicpack.net/