The civil penalties that can be assessed against the teens are compensatory damages (value of alcohol), plus exemplary damages ($150 or twice the value of loss) and costs incurred by bar in their suit against the teens.
The criminal penalties could include misdemeanor theft charges if the alcohol stolen was less than $500, with the possibility of a $1000 fine and up to one year in jail, and misdemeanor minor in possession charges, again with the possibility of a $1000 fine and up to one year in jail.
Misdemeanor convictions come with a whole host of other problems.
The bar potentially could have their liquor license suspended, depending on all facts (including checking of IDs).