I think it's a horrible challenge designed to put more pressure on mums (because frankly you never hear of dad's doing this kind of thing).
Spending more time outside is brilliant, but this 'challenge' is so restrictive that it's almost impossible for most families that with drunk time, to manage. Eating outside doesn't count. The school run doesn't count. Organised sport doesn't count. Its unstructured play time outside.
Their breakdown for June suggests 5 hours. IF you go and spend 30m at the park before school (who does that, lol) and you pick them up at 3.30, get home at say 3.45, that means staying outside until 8.15pm. If they wolf down dinner in 15m, they can come in to start homework/reading/relaxing/going to bed, at 8.30.
If because you work, your doing get home until 5.30, including dinner they wouldn't be in until 10pm.
No swimming lessons, no clubs, nothing.
Yes, you could do more at the weekend to knock a couple of hours off, but what a lot of pressure.
Its viable for non napping toddlers and preschoolers. That's about it.
Its more manageable if you break the rules and include all outside time, but i guys it wouldn't be a challenge then...