New Treasure Seekers - E. Nesbit

Oswald, Dora, Dicky, Alice, H.O, and Noel fill their free time with entertainments that don't always turn out as they plan. But whether telling fortunes at a fete, unwittingly assisting an elopement, reforming their nasty cousin Archibald or even getting arrested, it is all good fun, and usually in a good cause.