Have you considered other areas of SD such as North County or does it have to be RB/Poway?
I live in San Elijo Hills (zip 92078) which is about 20/25 minutes northwest of RB with my wife and 2yr old son. I would say most of the people that live on our street are in their 30’s and early 40’s. There are *at least* 30 kids on our street ranging in ages from 0 – 10 and quite a few stay-at-home moms. Our neighbors are super friendly, there always seems to be a weekend party somewhere, block parties during the summer, and the beach and Lego Land are about a 20 minute drive (though I have yet to go to Lego Land). My mother-in-law helps babysit sometimes and takes her 45 minutes from South OC. As a bonus, I’m only about 15 minutes from several breweries and Phil’s BBQ (a local fav that serves up the best BBQ I’ve found in SD so far).
Prior to SEH, we lived in Carmel Mountain/RB (zip 92128). My experience living there was that the families were on the older side, and kids were high-school+ aged. The location is ideal, centrally located to almost everything. We initially wanted to live in Carmel Mountain when we started looking for a home, however, all the homes we liked were out of our budget. At the time, we could buy a bigger, newer house in SEH for less. So far, that move has worked out great for us (though I had my doubts when I was having to commute to Mission Valley). Yes, we have Mello-Roos, but that only adds approx $150/month to our property tax bill.
RB is a nice area (I like Carmel Mountain), so I’m not trying to pursuade you otherwise. Just wanted to throw out another area that seems to mesh well with the criteria you listed. Best of luck on the move and the house hunting.