I absolutely hate having my bags packed at the supermarket!
I'd be very wary of giving money to anyone claiming to be collecting "for Manchester" other than an official charity, there are already plenty of fraudsters out there.
I agree with previous posters, some families will need financial help but some will wonder how money can help with their loss.
The idea of a park for children is great in principle, but the people involved came from all over the UK so it could not work in practice.
Surely better to give it to an existing charity that helps with rehab in case of life changing injuries, be it loss of limbs, of hearing or of sight. And victims' mental health is bound to suffer of course. You can specify that your donation is to be used for children I believe, though many victims and their families are obviously older.