First of all, ask them if they want to be thanked in public. Some people just prefer to stay out of the spotlights.
And it should indeed be balanced with the attention your other volunteers get; they contribute time, which can be even more valuable than money. You can thank them all together, or make some kind of recurring article in your website/newsletter ...
I understand that leader should be active
Yes, however beware of your activity. For nonprofits over 200 volunteers and various projects, it is impossible to handle every detail. Therefore it is important to have middle management reporting to you.
Communication is key and it should be adjusted to the various levels of the organisation.
why enthusiastic ...
In my experience, people are seeking leadership, organization and delegation of work, at least initially, to build motivation and momentum to start experiencing success as a group. Help them see the value of investing a wee bit of Individual effort and subsequently experience some collective success as a team.