The first month decides whether staff and volunteers see the site as help or as one more job. Spend the first week watching what people actually do. Which volunteers signed up for a shift without asking anyone? Which ones phoned the office instead? Every phone call is a note about something the site did not make clear, and fixing those notes early is worth more than any new feature.
In week two, send a short, personal message to every volunteer who has not logged in. Do not frame it as a campaign. Say what the site now does for them, such as showing open shifts and letting them swap a slot, and ask what would make it easier. A handful of replies will show you the one change that matters most.
In week three, look at the donation flow as a donor would. Make a small test gift, check the receipt wording, check what the donor sees afterwards and check whether managing a monthly gift is obvious. A donor who cannot find how to change a gift will cancel it, and the cancellation costs more than the fix.
By the end of the month, write a one-page summary for your trustees or board. Say how many shifts were filled through the site, what supporters asked for, what you changed and what you will do next. Keep it plain and honest. A board that sees steady, modest progress keeps supporting the project, and a board that hears only promises stops listening.
Also use this month to decide who owns the site after you. Name a second person who can post updates, approve volunteers and answer a supporter. A site that depends on one volunteer disappears the day that volunteer moves away.