I too agree with SFilak and Critter.
Prior notice for a large, unbudgeted expenditure is a must. To put this matter in the hands of as many members is the best thing you can do. I can imagine just as many problems if the BOD decided this kind of expenditure as a no notice vote.

Our Bylaws state that our Executive Board (Top 6 positions) can approve an expenditure below $100 without a full "Board" vote. In general, we have a very well thought out budget, so committee chairpeople know the amount they are dealing with. For any school requests, or any other expenditures that come up, they go to a full "Board" vote. This means that it will be brought up at a board meeting (consisting of executive board, and all committee chairpeople). Anyone who is a member can come to the meetings and also have a vote. We set it up this way, because when we were PTA, the board voted, and then it had to be presented at a general meeting for a vote as well. We didn't always have a general meeting every month, so many times things got way behind. Also, the general meeting attendees really had no insight into the workings of the PTA, so it was obviously just going through the motions.

IT's right in our by-laws that we can spend up to $50 with out a vote and we still mention expenditures at the meetings. I like to think we have $49.99 before we need to vote to keep teachers etc from asking for $50 on something we wouldn't normally approve.
The Prez this year has decided (with agreeance from the membership) to approve spending as we go...not sure about this but she has been able to keep a good mind about it.

We didn't put that in our by laws last year when we revised and boy do I wished we had!!! I always felt funny about any decisions about money I made with the exec board. I always got everyone's opinion too. Anything over $100.00 I took it before the general members. This years prez isn't informing anyone of anything. The treasurer asked me what was usually the budget on the float that she was asked to write a check for $115.00. The PTO has never before gave reimbursements for the float. This is just one of many indiscretions she has taken on, if the rumors are true.

I agree with SFilak. Our board has the right to approve up to $100 in unbudgeted expenses between our monthly meetings. Last year we had a large surplus from our fundraisers - about $4000 unplanned. First we asked the principal how he would like to see the money spent. We also asked for input from the members. After discussing options at a couple of meetings, we put the allocation to a vote of the membership.

I agree with the previous posters. Money UNDER a certain amount can be agreed by the board only but over a certain amount, it should be voted on by the general group. We send out our meeting agenda's a week before the meeting to the whole school. If there is something controversial, then people will attend if they have an opinion or if they want to vote a certain way.
It's kind of patronizing to think that the board knows what's best for the general group when it comes to the big money, but that you'll let them vote for the little stuff. IMHO...