I had "big plans" to add some more science to Little Hearts this year....but...
Here's the deal. Science is secondary to learning to read (and I'm talking about reading books fluently as my goal this year) and math. There just isn't time to add a bunch of "stuff" to our day and still keep it short and sweet as per the CM philosophy. So, science has taken a backseat.
Here's how we have added some science and still kept our day short. We look up info on the animals discussed in the Burgess storytime books. There are lots of animals in those books and we have found a coloring page to go with each one on the internet and we have plenty of science type books around here to find other info about them. We also keep nature journals and try to add to that at least once a week. Those two activities, along with the activities from Little Hearts have been plenty. Last week, we caught some frogs and looked them up in our Frogs of Missour book to correctly identify them and added that to our nature journals. This week, we went mushroom hunting and drew those in our journals....and had a feast by the way on morels!!! Yum-o!
I think it's fine to add more if you feel you need to, but don't feel discouraged if your plans fall through. If you plan to much into your day (I'm speaking from experience here) something will fall to the side and you don't want it to be reading or math.
I was a first grade teacher for many, many years, and trust me when I say, science and history are not big in K or 1st grade. We only had to schedule something for each 1x/week and that was usually Weekly Reader and a Magic School Bus video! Believe me....Beyond is above and "beyond" (my joke for the day

) what you would be getting in any ps classroom.
I think you should give it a shot before you add anything else just to see if you have the time (or need) for it.
And don't worry about asking too many questions.....you're probably asking something that someone else wanted to know about as well!

Mel