Hey Rudy we did the Mirror lake trail when we were there. Theres some other paved trails right near there, and Ben had tons of fun on all of them. Theres even a creek right by the trail where kids can get in if its a hot day. With two 3-year-olds Id say you shoul dprobably have a lightweight backpack or a jogging stroller maybe, so they can take a break if they dont want to walk the whole mile. I think you can take yur dog with you, since the trail is paved, but you cant let them off the paved trail. We really loved the lake and Yosemite, its a one of a time experience for kids, and I cant wait to take the little guy back