ICES Convention looks like fun, but attending is to better my business. But I'm going take my family to double it as a family vacation.

What should I declare as a business expense:

ICES Membership :$260

Classes: $75 each

Demos: $7 each

Gas

Hotel: $125 night for 3 nights

Food

Thanks for your help! 

Not knowing what the tax laws are in your area, I would think that the Membership, classes and demos are all a business expense.  The rest would be percentages, ie claim a percentage for your food, but not the full amount for your family etc.  You could check with your accountant to be sure.

I agree w/the other poster.

Clearly, the membership fee and class fees are 100% deductible.

You "can" declare what would be YOUR individual expense, and take off for the family. A hotel room is $125 if 1 person stays, or 4 (in most cases), so you can take the whole expense. Same with the car/ gas (as relates to the convention ONLY, and not "side" trips elsewhere like a museum or zoo). Food is the only thing I would "divide", as you clearly would not eat 12 meals a day.

This is great!  Would I log my mileage there as well? 

Assuming this is IRS we are taking about, the expenses would go in travel on your schedule C.

You should really be familiar with that form, whether you do your own taxes or not. You know what receipts to save. There are special addition forms for cars/ mileage and meals. If you only read one thing, read schedule C form, part II--- the middle of the page. Those are the questions/categories of expenses the tax preparer will need answers/receipts for.