It's important to point out that what you are asking your new leadership to do is pledge to act in accordance with your organizational values. You are not creating a contract with them. Therefore laws for electronic signatures really do not apply or matter here.
Because your agreement does not specifically state any terms, or define nonconformance with those terms or consequences, it doesn't even constitute a "bylaws" for governing your organization. How do you know if your leadership is acting out of accordance with the values? What happens if they do? What happens if most of the leadership votes to go a new direction that others feel is not in accordance with the values?
I point this out not to suggest you create complex bylaws to cover all these potential situations. I would only do so if the organization's operations are complex enough, or if there are a large constituency or budget involved.
What it seems you are really trying to do is the following:
1) Only recruit leaders who agree with the organizations core values, and discourage others who don't agree from joining.
2) Impress the new leaders on their symbolic duty to the organization and its constituency. This duty does not seem to be fiduciary, meaning that it does not carry legal impact to the organization, customers, or paying members.
To that end, I would suggest that a solemn pledge and ceremony might achieve this goal more effectively. Come up with an impressive promise that new members must raise their hand and recite. Have them do this in front of the whole voting board or even the entire membership publicly. Choose other ceremonial traditions that are appropriate for your organization such as signing a history book, conducting prayer, or giving or receiving certain symbols.
