We had a Living Social voucher for San Diego Whale Watch, and went on the tour with our 2 girls, aged 3 and 8. We were a little worried it would be difficult with the kids, but it really wasn't and they enjoyed it as well (except it got a little long for them). We saw dolphins, a pod of seals swimming and a fin whale during or trip.
It was mid-December and about 60F when we went out, but it can still be super cold when you are on your way out and against the wind. Plan ahead and bring, warm clothes - pants, jacket and gloves for sure. We also brought hats and scarves and blankets for the kids. The blankets felt really good going out, and then once the day warmed up a bit more and the boat wasn't moving so fast we were able to take our jackets and warm gear off and be comfortable.
The day we went was very clear and calm, but we did take motion sickness pills in advance just in case, which I would recommend. There is a place you can go in to get out of the wind if needed, and you can purchase snacks, coffee, and hot dogs on the boat, although it is a little spendy. You can also bring your own onto the boat. The crew was great and the boat was clean and comfortable - plenty of room for everyone. The captain and naturalist worked very hard to find some wildlife for us, staying out a little longer to watch the fin whale. I highly recommend this attraction!