AHej, im new to this so hope you can help :) Im gonna make a cake for 30 people, with fondant. I thought i would make sheet cake. And i would use the tray in the oven for the baking pan. So im thinking of making a chocolate cake. So here comes one of the question. Do i put baking powder in the batter? And do i put baking soda in it? Beacuse if i put baking powder in wouldnt it rise to much and overflow. If you have any recipies for a good chocolate or vanilla sheet cake i would love to get them :) the second question is im gonna make 4 sheets so 4 layers of cake. How much rasberry mousse filling do i need? The third question is. How much buttercream do i need for crumb coating the cake? And last question is how much fondant do i need for the cake? Thanks for the help :)

You really need to purchase a standard sheet pan. For 30 people and your cake being 4 layers high, you really would only need a 9 x 13 pan. 

It's hard to say how much filling you need. One good rule of thumb is to make what you think you will need, but double that recipe. It's better to have more filling than not enough.

The best way to fill your cake layers is to measure the amount of filling for each layer so they are all the same. It will make your cake look better when you cut into it. 

For your buttercream, make a double batch as well. 

It's also hard to say how much fondant you will need. After you do this for a while, you just know, but you always plan to have extra on hand in case you have to re-do it! I would plan for at least 5 pounds of fondant. 

You need to find a recipe you think you can make or use a boxed cake mix. You can't just leave out baking powder or baking soda because you don't want the recipe to rise too much. You will end up with a disaster.