if you want to give a "favor" to everyone... you could give an inexpensive toy to each kid (like a cheap stuffed animal or little "lego" people (the toddler ones not the swallowable ones). Or maybe toddler crayons and some coloring pages.
Or send every kid home with some home-made snack that is relatively healthy, like granola bars or oatmeal cookies, or muffins.
Really, it all depends on the kids you invite and thier parents. I have been to parties where the parents are pretty relaxed and would be happy with any cute thing... and some parties that parents are anti-sugar, anti-mess, and by-the-book parents.
It is better to just have a good party that to get too caught up in the favors. Junk will probably get tossed anyways... so only worry about it if you can afford to do something nice (ish). On the other hand I thing that it is ridiculous to spend more than a few dollars on other people's kids AFTER you have fed and entertained them. Sure they were nice enough to come and maybe bring a nice gift, but you can repay them (with a gift) when you go to their kid's toddler party!
At least in my town the 2-year old birthday extravaganza has been blown WAY out of proportion. I am wondering if the parties are more for the parents than the kids anymore anyways. Just make sure the party itself has fun, simple games and activities to keep the kids happy, and you'll all have an awesome time!
Happy birthday to your 2 year old!!!