Terri, your follow-up makes it clearer: two agendas are going out, and the one the members actually receive is the president's edit. Two questions hide in there: who sends the notice, and what it must contain. If the bylaws say the secretary serves all meeting notices, the president issuing his own version is a bylaws problem the board can fix by vote at its next meeting: one agenda, sent by the secretary, and the president's additions go into your draft before the posting date, not into a separate notice.
The spending question is an open-meeting question, and ElleN has the core of it. Civil Code 4920 says notice of a board meeting goes out at least four days ahead and must contain the agenda. Section 4930 says the board may not discuss or act on an item at a nonemergency meeting unless it was on that agenda, with narrow exceptions (an emergency finding, a two-thirds vote on something that arose after the agenda went out, or an item continued from a meeting within the past 30 days). An item that appears only on the president's rewritten agenda is open to challenge.
The practical cure: put the spending item on a properly noticed agenda, ratify it at the next meeting, and record in the minutes which notice went out, when, and from whom. If the amount is large, a quick read of those two sections with your association's attorney is worth the hour.
ā Eli