Im recently start a campaign (my vert first try as a DM) and I decide to make some changes.
Generally, I recommend against first timers changing things. Stick with the basics, you will have enough to worry about.
I've been playing since 3 edition and the races description didnt change too much besides stats).
So my first question is why dwarf and gnomes get +4 dodge bonus agains giants. Dont know if this is a silly question, but yes im planning to remove it.
And elves: why they dont sleep. Why they got bunos saves agains enchantments.
These are relatively minor charges. Giants have always been the traditional enemies of dwarves and gnomes. Elves have always been seen as magical, but resistant to the charms of others. There is much history in these small bonuses.
If you take away these small bonuses you should give them something small in return. So Giants and dwarves aren't natural enemies, what is different about the dwarves in your world. Elves aren't immune to charms but what else is different about them. Maybe the dwarves and elves are enemies in your world (kind of wood elves vs. the dwarves), so give them hatred bonuses like the current dwarven orc hatred or bonuses to sense motive because they are suspicious of each other.
If you want them to be different make them different, but if you take something away you should add something in return.
I agree with the guy some call Tim, as a first time GM I strongly advise against mucking with race or monster stats. You're going to have to much else to deal with repercussions of balance issues.
If you are hells bent on modifying them I suggest you look at the Advanced Player Guide. Dwarves can replace their Defensive Trainig with Deep Warrior, which just shifts the bonus to aberration typed monsters. Gnomes have 4 replacements, Eternal Hope, Gift of Tongues, and Master Tinker, and Warden of Nature. Elves also have a few options, Dreamspeaker and Lightbringer.
There are better ways of making a world different the modifying racial stats. If you never looked a Eberron I suggest you do that. 3.5 Eberron was built basically from the ground up to be a 3.5 setting with all the core book stat assumptions. Even still it made some very interesting societal distinctions.
( I accept Translated by Google, to be a fair excuse. :D )