One strategy I use in outreach is going for groups and organizations that already have "buy-in" or reason to be looking for the same things I am - engagement.
It's the beginning of the school year, perhaps there are Boy Scout and Girl Scouts in your area looking to work on final projects, and they could collaborate in the process. Honor Society, other non-profit organizations, and even college applicants in general often have a volunteer expectation or "requirement", and getting youth who already have a reason to complete these experiences can perhaps motivate some of the adults to collaborate further. (Additionally, sometimes when people "have to" do volunteer work, they find that they enjoy it, and continue even after any incentives dissipate.)
People have a tendency to assume other groups are a timesink or competition, when the reality is that a lot of these organizations are already well-connected to people who value the same things we're working towards! Even if they themselves cannot commit, often they will know several other people and organizations they can spread the word to, or folks they can nominate as good contacts to follow up with.
Youth groups generally are a good start, but there also might be community and resource centers, services that help with families and childcare, science and nature clubs in the local school districts, or even child care services looking to do field trips or have guests to do on-site demonstrations! (For example, our CCE was at an event the day before Mother's Day, so seed planter demos for kids and families were a HUGE hit.)