Best music festival for a 4yr old?

[SuperBunny]

I want to go to one but have never been. I thought DS and I could go as our summer holiday next year.

My criteria:

Relatively small, not overwhelming
Good music & other stuff to do

Preferably in the southwest-ish & ideally on a weekend during term-time.

Was considering:

Bestival @ Lulworth
Larmer Tree
Womad?
Cropredy?
Beautiful Days

My DP works at the festivals. He says both punters and crew rate Beautiful Days and Camp Bestival (not the usual Bestival) as the best kids ones. The organisers of both have lots of kids and really know what they're doing.

Ok, that helps, thank you!