Turn already brewed half batch into a full

Today I went and bought a REAL brew kit. I have a half batch of English Brown Ale workin (in my MR. Beer). Also, today I realized I screwed up and put all the grain, instead of half, into the first batch. So I'm going to supplement the rest of the ingredients, incl.: water, DME, LME, yeast and hops, into the first batch.

I'm gonna start by boiling 1 gal fresh water with the DME and LME and introduce the hops as originally directed. Then I will add the wort to cold water and mix. Then I'm going to introduce the old batch of Ale in to the new wort and give it the rest of the yeast. Basically I gonna just treat it as if it were a brand new 5 gallon batch all together.

Any thoughts?

Experimentation is good. Expect to destroy things; be impressed when you don't.

But I'm a noob anyway