There are no official cheats for Worms World Party yet, but I have found a very easy way to beat missions.  Not a lot of fun to use this method, but if you are stuck you can use it:

1. Go to the /data/missions folder.  There are files that you can change to make missions easier.

2. Any mission.wam file can be opened in NOTEPAD.  There is all the info about the mission (Tip:  You should probably backup all of the .wam files before trying this, or at least the one you are working with).

3. If you scroll down to [HumanTeam], there are a few things that you can change.  In the mission1.wam file there are two weapons that you have.  The girder and the bazooka.  If you wanted to have unlimited amount of girders you would set it equal to -1.  You can also change things such as the Worm_Energy, so that in the mission you have lots more energy. (Tip: I do not recommend changing something that you do not know about.)

4. You can change other things if you know what they are.  Here is a list of weapons and items you can give your worms by putting the command in the .wam file und other weapons (the # symbol is the number of items you want your worm to have...-1 is for unlimited):