Yes, you can definitely introduce engineering to early grades. Young kids are so creative and really enjoy figuring out how things work. I suggest starting with a material exploration (sensory experience) and then engage them in solving a problem using what they know about the properties of materials. For example, allow kids to see what types of materials float and which ones sink. Then ask them which ones they could use to create a boat. Once they test their boat, allow them the opportunity to revise their design and test again.
If you're looking for a curriculum to try out, check out Engineering is Elementary:
The website has lots of videos that may give you ideas too.
Hope this helps!