not unreasonable at all to lay down some ground rules, i wish we had done this with our first two!
with ds1 i had a nightmare end of pregnancy, hospitalised with spd, failed induction at 38wks, then induced once past dates, a nightmare 3 day labour and i was knackered, i was told NOT to get out of bed by drs as my pelvis had seperated too much and was in a lot of pain from that and an episiotomy yet my dps relatives (mum, aunt and her husband) turned up the next day and stayed for ages, passing the baby round etc whilst i was tired, emotional, in pain and trying to get to grips with bfeeding etc. it was made worse by the fact that i was just 20 and i had only met the aunt and her husband once before for all of 20mins.
at one point i had to get up to go to the toilet and shuffled off in pain, i enede up crying, a midwife saw me and immediately knew what the issue was and she went back and told the relatives they needed to go so i could rest! yay! but when they went they insisted on taking dp with him so they could all go out for a meal and spend the rest of the day with him, so i was left alone, stuck in bed and barely able to pick the baby up! :(
with ds2 i came home from hospital asap after birth, quick easy delivery, but still had terrible spd, they again turned up the next day, at our home this time, and stayed until late at night, it was about 10pm and they commented that i looked tired! well yes, labour started at midnight, ds2 was born at 7am and you are still here, so we are sat entertaining when i should be in bed!!
they also brought their dog, i am allergic to dogs!! 
with ds3 it was easier as he was born just before xmas and the weather meant they couldnt dahs over and we said that we wanted a a week or so on our own, they were most put out!
ds4 again we said wait a week or two, in the end the aunt was so cross that we wouldnt let her come in the first week that she refused to come for 6 wks, her loss.
and with dd we asked for them to wait a bit as well, this time there was a bit more discussion and i tried to explain our reasoning for wanting a bit of time, but basically got told we were mean for not letting htem see the baby when it was 'new' i mean a few days old or a week old, its still new ffs!
but then these are relatives that turned up at the bedside of another new mum within 4hrs of her having a c-section, 6 of them all at once and hung around for ages!! so they really dont get it!