being a pastor's wife, i am often in this situation, sometimes entertaining people really last minute. and with a toddler in the house who owns toys that seem to multiply at night, yeah, it's hard to keep the place straight!
one thing i was able to do in terms of keeping the house neat - i try to clean up the kitchen counters every night. it makes a huge difference. also, i keep Josh's toys put back on shelves or in the den at the end of the day(it's the room off of our bedroom that visitors don't go into). if someone was to come during the day and surprise me with toys in the front room, i would just ignore the toys - it's obvious to anyone that we've got a toddler, they should expect to see toys out when Josh is awake.
in terms of being able to be a good host/ess and be hospitable... no one expects Martha Stewart! and if they do, they themselves need serious help

i usually have a box of cookies (or lately, a container of homemade cookies) and we always have coffee and tea in the house.
i have never really had to worrk much about being alone with someone - because it's usually dh doing the last minute inviting, so he's usually there. and if i felt uncomfortable for any reason when he wasn't there, the church is exactly 7 minutes (driving) from home, so he could easily come home quickly.
we are careful about who stays overnight at our house - not just for our safety, but because we have a child. usually it's family, and this year we will probably have a missionary staying for a few days during our church missions conference.