I've just seen this having come back from Glastonbury and know I'm a good few years late replying to the original poster but thought I would anyway.
So there is a way to "do it posh" these days although flushing loos are out of the question. What you're after is a Worthy View pre-erected tent. This is a specific area atop The Park area where tents, cabins etc. are pre-erected for you and you just rock up and camp. There are hot showers available 24-7 although the loos are portacabins and trust me, portacabins get blocked up whereas the site's longdrop loos are far more humane!
However, having just done my first Glasto in family camping, it's not all that bad. Okay, so hot showers was the one thing I was really missing! But for all you new parents who might be considering summer festivals, do have a read of an article I wrote on taking a baby to Glastonbury: http://rockshot.co.uk/27557/feature-tak ... -festival/