Two year olds are a lot of fun, but hard to play games with. The good news is that it doesn't take much to amuse them.
You could try a version of musical chairs, where you turn on music and they dance but have to stop when the music stops. Up to you whether you think they will understand, or want to, sit out if they kept moving after the music stopped.
You could also do a craft of "my favorite things." If you have catalogues and magazines, you can cut out different things that the kids would like -- toys, flowers, airplanes, smiling faces, etc. Have enough for each child to choose a few. They can paste (glue sticks might be good) their favorite things onto a piece of construction paper to take home with them as a party favor.
You could also get a paint with water book from the Dollar Store and have them do that page as a craft.
You could have balloon volleyball. Get a regular balloon and blow it up yourself -- not helium. Have the kids bop it around the room and try to keep it off of the floor.
My mom gave me a good piece of advice when my kids were little. You need to have somewhere to go. In other words, you can't have huge, blowout parties every year. Those parties become the norm, and each year you will want to get bigger and "better" to top the last. Save the big parties for when the kids really want one, and the age suggests it's time. For example, 10th birthday (double digits), 13 (a new teenager), 16...you get the idea.
My mom also reminded me to keep the activities to the age; the point of the party is for the kids to have fun -- no need to impress the parents.
Good luck with the party. It will be fun if you have a little fun as well.