What exactly are you looking for in terms of advice? Which hops to use with each other? How to use them together to build the hop schedule? Are you looking for advice on the malts or is that just informative? Happy to help but just wondering exactly what you want/need here.
My initial thoughts for the malts are that the pils and oats would be fine. Could you add more things? Sure. Do you really need to do that? No.
For the main three hops those all go together great. They are all crowd pleasers. El Dorado and Idaho 7 are also great in my opinion but I think you'll find more mixed opinions on them. You could use either with these other hops but at some point there will be too much noise in the beer for you to notice.
I would definitely use some Citra since it's for a party and almost everyone is going to like that. It's great to support other hops as well. Use one or both of the others in whatever amount suits you really. I just did a cold IPA with 50/50 Citra and Simcoe and it's great. I've done various combinations of all three and is really is hard to go wrong. Here's a thought for the hop bill using what you have.
1oz each Citra/Simcoe at 5 mins
2oz each Citra/Simcoe for 15 min hopstand
4oz each of Citra/Simcoe/Mosaic dry hop as krausen falls
Simcoe is a solid bittering hop too so you can drop some in at 60 mins to get the bitterness you want. It's such a great aroma hop that I'd save it if you have something else for bittering. If you don't want an ounce of Citra left over then just use it in the dry hop and drop an ounce of one of the others. Or just keep both if you want because I'm not your boss