Depending on the 14 year old's maturity.
I used to leave ds (3) and dd (1) with a 14 year old who was extreemly mature (seemed like she was 25). She had a sister who was the same age as my dd so knew exactly how to look after a bub. I was very comfortable with leaving them with her.
If your baby sitter was similar then i would feel comfortable with leaving my 2year old in her care especially knowing her parents are next door (whom I am sure will pop over to check on her anyway)
Not sure if i would leave my 8 and 12 year old children alone. Only you know their maturity. If you do is it possible to ask the adult neighbours to pop over a check on them before they go to bed and give your kids the adult neighbours phone number.
1 adult probably should stay sober incase something happened and you were totally aware.
If you have dinner prepared, a few movies etc I cant see to much of a problem. Would also depend largely where you lived and what your suburb was like to I think. I lived in the city and my house backed onto a park and wouldn't have felt comfortable but now in a small town I would feel fine I think.