1. e4 e6 2. f4 ... huh? what to do?

knight to d5

15...Bh5 still looks good to me

Heh. You should've played him again and showed him what's what. However, if you were humoring him-it's understandable. But as far as getting advice on beating an 8 yr old in this variation, heh, forget it!

8)

1. e4 e6 2. f4

It's not something that I would play, but it looks like it should be a pretty common opening to me. It follows opening principles, and looks sort of similar to the King's Gambit.

You didn't lose because of the opening, you lost because you missed a very simple tactic. 

After Nf5, you probably should have stopped white's g4 (which was never played in this game) with h5. Also, you may have rushed castling a bit. You could have built up a big K-side attack by postponing castling and perhaps even castling Q-side. 

But your position was fine for a long time. You just missed a tactic.

simple tactic

Smart 8 year old. He took you out of your preparation

There is nothing wrong with losing to an 8 year old. There are plenty of 8 year olds out there that are quite good at chess. 

I ran your game through lc0, you were in a winning position until you blundered by snatching the pawn which was protected twice. Once by the rook, and once by the queen indirectly with the Qxe6+. You should have seen that your pawn on e6 was unprotected and would give a check when he took it, allowing him to take your knight.

When playing children (or anyone for that matter!), never underestimate them, if it looks like they blundered a pawn or a piece, make sure you calculate it out and look for all the checks before snatching the pawn. I think you need to be careful snatching pawns in general, there are loads of gambits that will catch you out, and queen traps etc.

An 1800 rated player never heard of the kings gambit.  Right.  

Edit: posted in 2013.  How did I get sucked into this?  

15...Bh5 is still perfectly possible. Discuss.

In meaningless internet games and nothing more, as far as I know.