I think you should use this and screenshot it at the end so everyone knows it was fair and random.
Random.org Instructions wrote:Let us assume you have sold or given out sequentially numbered lottery tickets, e.g., numbered 1-250. Then do the following:
Go to the Sequence Generator.
Type in 1 as your smallest value and the number of tickets sold as your largest, then hit the submit button.
On the resulting list, the first number is the number of the winning ticket. If you have a second prize in your lottery, the second number on the list is the number of the second winning ticket, and so on. Discard any unused numbers.