You really need to check your state laws on these questions and I would also check with your local DA's office and even your state attorney general's office.
I have found in the past that it pays to do so as you will talk to the officials who will sue you if it turns out your are involved in a lottery and you will find out from the "source" exactly what you can do and can't do.
Many years ago, I contacted the consumer fraud unit of the Vermont AG's office to verify that a local branch "contest" that involved having existing customers drop their name in a bowl for a free lunch if they brought a non-customer into the branch to meet with a bank officer (no requirement that the non-customer open an account or obtain a loan and no requirement that the existing customer do anything as well other than just bring in a non-customer to meet with a bank official) did not constitute a lottery since there was no "consideration" involved. I was told that the Vermont AG's office took an expansive interpretation of "consideration" and that "consideration" was involved because the bank was making its customers "do something" (i.e., contact and bring in a friend into the branch) and that if the bank proceeded with the contest it would be criminally prosecuted.
I thought the opinion was ridiculous and extreme, however I was talking to the assistant AG who initiated lawsuits to enforce the law. Rather than to take the opportunity to fight this extreme interpretation in court, the bank decided not to go forward with the contest.
Since then, I have called consumer fraud prosecutors from time-to-time. I never have had a repeat occurence in receiving what I thought was an extreme opinion, but I have received a lot of "tips" about gray area issues and have been able to make some minor changes to planned offers to avoid getting close to those gray areas.