This looks good. Here is a conversation I had with a fellow translator soon after I submitted:

B: Regarding 幹事さん必見!最大100人収容の掘りごたつ座敷での宴会はいかが？
It might just be sunken seating at the restaurant...

R: If they are called 掘りごたつ, doesn't that mean the restaurant has (sunken) kotatsu? And don't kotatsu (sunken or otherwise) necessarily have a heat source?

B: The meaning may be embedded in the term but no, I don't believe that out of doors it necessarily implies heat. It can be used to refer to the structural form. Whether this is correct or vulgar is uncertain.

R: I see. Thanks. I wouldn't know personally, but the Kenkyusha definition suggests that they have heat sources.

B: I don't think there is a more direct way of stating that there are seats where the leg space is below the level of the floor and there is a table on top. Maybe there is. Sometimes there's just nothing in the pit. This should still make it the same.

@@ -28 +28 @@
-<gloss g_type="expl">low table over a hole in the floor (may have a heat source underneath and a covering blanket to retain warmth)</gloss>
+<gloss g_type="expl">low table over a hole in the floor (may have a heat source underneath and a hanging quilt to retain warmth)</gloss>

掘りごたつ returns much different looking google images than こたつ (i.e., no blanket and often no heat source, though this may be simply because they want to emphasize the architecture).  dictionaries do specify the presence of the heater, which is also what i would assume is true of a こたつ.

@@ -26 +26,3 @@
-<gloss>low, covered table placed over a hole in the floor of a Japanese-style room</gloss>
+<xref type="see" seq="1194360">炬燵</xref>
+<gloss>sunken kotatsu</gloss>
+<gloss g_type="expl">low table over a hole in the floor (may have a heat source underneath and a covering blanket to retain warmth)</gloss>

Shouldn't it be mentioned that the tables have a heat source? Or is this not necessarily the case? The GG5 entry seems to imply that 掘りごたつ have a heat source:
こたつ【炬燵】 外字(kotatsu)
a kotatsu; a low table with a heat source (usually electric nowadays, but formerly a pit of hot coals) underneath, covered with a quilt to retain the heat, used for keeping warm in the winter, as people sit around it with their legs under the quilt; 〔置き炬燵〕 a (portable) kotatsu; an electric kotatsu; 〔掘り炬燵〕 a sunken kotatsu.
.
This EDICT entry could also benefit by being linked to the entry for こたつ, I think.