Kazgran great news.
Don't worry, so long as you are welcoming and don't interfere too much, things will work out just fine.
We have GC in the same village, next village, 15 miles away and 80 miles away. The local ones do the popping in thing, which can be a pain but I don't complain as lots of people on here would love that! The ones 15 miles away I look after one day a week and sometimes they stay here. The one in London come every 6 weeks or so for the weekend and we skype in between. Part of the reason they come home is because DD2's brothers and sisters are around and we get the benefit!!
We have made our spare bedrooms multi purpose so the GCs come and have their own room but when 'grownups' come the decor is not too babyish. we have a travel cot, high chair and lots of toys. DH remarked that we seem to have more baby stuff around now than when ours were young. 