Payment handling for INTERNATION.org Groups (Hong Kong)

I know many groups encountering problems on collecting and counting payments when organising activities.

I have similar experience and know the organiser will usually ask:
1) Should I ask the people joining to make payment in advance, so that i can secure their attendance and the activity get enough fund to run?
2) If I do "1", does this mean than I am doing something mean and expressing that I don't trust them (traditional Eastern Point of View)?
3) If I let the people joining paying after the event, if they run away or "forget", what should I do? Can I chase the debt? If I do, I must be thought I am a very mean and greedy person, this will hurt our friendship (very traditional Eastern Point of View)

For this reason (しょうがない）, I am trying to consider several ways to solve the problem:

1) As I know, joining service of Internation.org can make use of "paypal", I was wondering if attendee can only secure their joining in the activity after confirmation of payment by paypal.

2) Having own currency of Internation.org (Like value in Octopus). Member can buy internation currency by credit card or cash through ambassador who records their payment and increase their value of internation currency in their membership account. Then every time when joining the group activities, members can make payment through this system. If they don't do it actively, our internation admin can deduct the value from their account with authority they are having.

3) Use Internation Cash Coupons (or stamps), member can buy such cash stamps in activities held every time, and they can post the stamps by mail or letter to make reservation in advance.....The first activity may be paid by their Internation Friends' stamps or coupons.

Well, those are the ways I am just thinking.....

What is your idea?

Cheers,

Jonathan