Some design challenges that can be adapted for math/engineering use
https://dschool-old.stanford.edu/groups/k12/wiki/956b6/Design_Thinking_Projects_and_Challenges.html These challenges are created by the Stanford design thinking projects and offer good whole-group and small/individual opportunities for math and engineering extensions. You may need to add numeracy in terms of weight/height/material amount requirements to build in some math calculations