First time brewer looking for input on Recipe

Style: Southern English Brown Ale - 11B

Specialty Grains:
1.5 lbs Crystal Malt 60L
.5 lbs Chocolate Mate 450L

Fermentables:
5.75 lbs Dark Liquid Extract 17.5L
.25 lbs Dark Brown Sugar 50L

Hops:
1 oz East Kent Golding (5.7% Alpha) 45 min boil

Yeast:
WL005 British Ale (1.25L starter)

Equipment: 4.25 gal brew pot

Plans are to soak the specialty grains in a BIAB at 156F for 45 min. Pre-boil volume is 3.25 gal. 5.5 gal in the Primary (6.5 gal carboy).

I'm also thinking of adding 4 oz of cocoa powder to this recipe ...

Plan on brewing today, so I would like some input before starting. I'm nervous about my first ever batch ...