Dungeon Mastering for only 2 people... help!?

I wouldn't worry about it.... you sound more than capable. I always felt it often more difficult to run a larger group vs. a smaller one. You could always run a NPC healer, etc. However, that can get annoying and you can often forget about the character. I'd say start out small and see what the group does. If they get in trouble with no healer... you can always have them stumble across a body with just one last gulp of a healing potion dangling in its hand. Then it always becomes a fun debate over who gets that last sip, etc. You could always have a NPC group in the dungeon ahead of the players. That way they may find bits and pieces of equipment as they trek through and/or come across already wounded monsters This way, if the monsters are too difficult... you have the power to already say that the creatures only had half of their regular HP's due to previous fighting, etc. Plus, dungeon creatures can always fight other dungeon creatures as well... its crazy and dark down there!