Yes, knitting more loosely is going to give you larger squares. Ordinarily you could compensate for that by knitting fewer sts and rows or by going to a smaller needle. If the squares are only a bit different and you're using wool, you can block them all to size. I'd definitely block the squares and then for good measure, block the blanket too.
It's so hard to stop once you start knitting isn't it? I think we all understand that. You're right to take it slowly though, since things are feeling pretty good so far. I hope we get to see a photo of the finished blanket. Sounds lovely.