Set a minimum and maximum, choose how many numbers you want, and decide whether repeats are allowed. Numbers come from your browser's cryptographic random source rather than a predictable pseudo-random sequence, and nothing is sent anywhere.
They come from the Web Crypto API, which draws on the operating system's entropy pool. That is the same source used for cryptographic keys, and it is far stronger than the Math.random() function most simple generators use.
Yes, it is well suited to it. The draw happens in your browser and nothing is recorded, so take a screenshot or a screen recording if you need to show entrants that it was fair.