As mentioned above, it depends a little on whether those 4-cans were in the course of one full day or right over dinner. Assuming the latter, seems to me you and your partner were pretty spot on in your reaction and dismay. I can't know for sure since I wasn't there, but their response to you was quite childish. Being dry and angry with them without actually sitting down and having a discussion about it is a little immature as well. It's good you finally were able to talk it out even if the end result wasn't great. If they can't see the problem with driving children while under the influence, that's on them. Not on you.