Sequoia bayview trail at JMP (Joaquin Miller Park). 20-30 minutes drive from El Cerrito. Mostly flat, easy-peasy.
Crocket Hill, Soaring eagle trail. This is a 1.9 mile downhill. One need to first climb up along the firetrail, need a tow-line or geared bike. There is little or no shade, better go when it is cloudy. The parking is a bit tricky, either one parks at the park parking lot and do a lot of climbing along the edward trail, or park by the high way and take the short cut.
China camp, easy parking, intermediate trail, moderate climbing. Upside is that the trail is flowy, no roots or rocks, and one can play a bit in the park afterwards, Also lots of shadow.
Big Tree trail at JMP. There are some climbs and down hill, nothing crazy. you can push the bike in the worst case. It is a bit steep towards the end, but mostly ok.