I've done it several times now with dd and she loves festivals more than I do! She has always been pretty laid back in terms of where she sleeps etc though and once she's asleep very little will wake her.
When she was the same age as your baby I had her in a snuggly snowsuit and ear defenders in a moby wrap sling on my front under my big coat and kept to the back of the crowd and she slept through the whole evenings line-up without waking once. We bought her a really good quality three season sleeping bag and she slept in there snug as a bug. Good job really as it got down to -3 overnight one night! 
That said, we do have a vw camper, which means we are warmer and more comfortable than we would be in a tent and it means we have somewhere warm and dry to retreat to when/if it rains. It also means we can take shedloads of bedding and blankets with us and we have the awning for her to run around in, even if the weather is bad.
We took her again last year at the age of two and this time she slept through the evening line-up snuggled up in a sheepskin lined foot-muff in her all-terrain pushchair - actually she was one of several 'parked' along the outer edge of the tent with mums and dads taking it in turns to dance or guard the pushchair. 
We're going again in May this year and she is already talking non-stop about it. She'll be just under three and a half and I'm thinking it will be harder now than it was when she was tiny. We are still taking the pushchair, as she is small for her age and we can use it for her to sleep in for the evenings again. Next year we may have to invest in one of those little pull along wagons, as there's no way she'll agree to get in a pushchair by then, whereas despite not really using anymore, she's still quite fond of it at the moment.
I would agree with others that have said you need to consider if you're going to feel left out while all your friends are getting boozed up and in the party spirit. We are old duffers more sedate these days, as are our friends, so its not much of an issue for us, as we just go to enjoy the atmosphere and music rather than seeing it as a huge party, iyswim. We tend to meander back to the camp site before the music stops, have a quiet drink/chat with our mates and nosh down whatever curry/stew one of us has brought along from home or have a bb1, rather than staying up and partying through the night.
Another thing to consider is, if there will be anyone to leave your dd with when you need the loo - seems like a small thing, but if all your friends have been drinking, will there be anyone you can trust to leave her with while you negotiate the dreaded portaloos?
I don't know anything about Rewind though, so can't advise about that specific festival. The one we go to is very family friendly. There are almost as many children as there are adults and lots of baby and family friendly facilities.