Took my 7 yo daughter to her first game last night (she has been to the stadium before to watch City v United women), and she loved it.
I used to have a seasoncard, but gave it up 3 years ago and the cost for single games and availability make it difficult to go regularly. I tend to buy singles off FB if I go to any. I'm not paying £70 for two memberships for a start, so having these on open sale and relatively cheap meant it was the perfect game to take her to.
I wouldn't say she is massively into football, but she takes an interest because of me. Kind of wish i still had my seasoncard and I could take her more often, she might get really into it then.