Last year I ran a pool at work that had a full pack of $5 NY Lottery scratch off tickets as the top prize. (100 tickets were included in the pack which was wrapped in clear cellophane.)
When I purchased the entire pack of tickets, the big thing I learned was that the tickets had to be "activated" (by the retailer) because if they weren't, any prizes won could not be claimed. This is done to protect retailers. If a store was burglarized and an un-opened pack was stolen, the thieves couldn't win any money because packs are not activated until they're ready to be put in a display case for sale. (Not to mention it would lead law enforcement authorities right to whomever stole them!) If you're not planning on buying a full pack, this wouldn't be anything you need to be concerned about.
While I don't know how you plan to award prizes, I found that having a full unopened pack of $5 scratch offs was a powerful motivator towards selling all 100 squares in the pool. Each square costs 5 bucks, so I re-grouped the initial $500 that I fronted to buy the entire pack. I didn't have to front the money, I could have simply sold all 100 squares, and then gone and bought the pack, but it sure was a lot of fun seeing the expressions on peoples faces when I showed them the pack!
I should add that I made sure that I bought a pack of tickets for a game that had very recently been introduced, so I knew that top prizes were available.
The guy that won the pool told me he won approximately $220 in winning tickets from the pack. G5