An investment club is sometimes a social activity but all of your members should understand when they join that it is also a business. It requires regular attendance and participation by all of its members. In addition, if you have members who do not participate, you may lose the ability to consider yourself an investment "club" and may have to operate as a more sophisticated type of investment partnership. You might even need to register with the SEC. You can find out more information about SEC requirements here.
Of course, there will be occasional times when everyone has to miss a meeting. The wording provided here gives fairly lenient guidelines for attendance requirements. If someone misses meetings more frequently than this, they probably are not really committed to being part of your group. It's better to recognize that fact and let them resign than try and penalize them into coming to meetings. Some clubs think it will help to charge late or missed meeting fees to members who don't regularly attend. In our experience, these do not help remedy the situation so we do not recommend you do that.
Disclaimer: statements are opinions expressed by bivio Customer Support and are not official statements from any government agency. These statements are not intended to replace professional legal or accounting advice. When in doubt, follow the advice of your lawyer or accountant who is familiar with your particular circumstances and the laws of your state.