So, I've got quite a bit of experience of this and have dipped in and out of the festival a few times due to childcare commitments. What with having loads of kids and all that.
Living just outside Andover (NW Hampshire for those who don't know) and being about an hour door-to-car park field away obviously helps.
Bearing in mind I'm a Tuesday night queuer, in recent years I've:
1. Gone down Tuesday evening. In and set up by 8am to 9am-ish on Wednesday. Spent all Wednesday day at the festival and gone home on Wednesday night. Actually went back to work on Thursday (utterly bizarre) and then me and Mrs Woffy went back down on Thursday evening when we had child care. Left late on Sunday, quite a bit after the headliners. Meant me not drinking on Sunday (which wasn't the worst considering my consumption over the previous days).
2. Same as above but picked Mrs Woffy up early on the Friday morning.
3. Both arrived Thursday during the day. Mates set our tent up for us after queuing on Tuesday night. Swerved the horrific weather getting in that year: 2016?
4. Last year Mrs Woffy was 7.5 months pregnant and put her ticket back in the pot. But she and my mother in law dropped off mini-Woffy on Sunday morning. I'd packed my stuff up shitting early on Sunday, wheeled it to the bus / Gate A on the pushchair. Met them at B&W Showground. Dropped stuff off, brought mini-Woffy and pushchair (+day rucksack with stuff for a 3 year old) back to site and had a brilliant Sunday, although 6 hours in the Kidz Field. Again, didn't drink on the Sunday but didn't mind.
If you can do any variation on these and need more details, let me know. If you drive home / away from site and then drive back you often feel like you're gonna be parked miles away. But with minimal - if any stuff - to bring back in again it's a doddle: walking an extra field of car park is nothing compared to lugging a tonne of stuff for 5 days. Plus you can bring booze in with you piecemeal rather than all in one go.
Thursday evening (in time for a decent night of fun) until Sunday post headliners (3 nights) is pretty decent if you can manage it.