Here is the quick and dirty list of my favorite activities for this age: 
🧡Pre crawling! Pivoting & reaching for toys to the sides help strengthen the arms and prep for crawling 🧡Belly crawling forward: If your baby is pivoting in a circle, try bending up one leg, holding the foot steady and then letting them push forward 🧡Core strengthening: happy baby’s reach to their toes for core strengthening! Try connecting ribbons, necklaces or link toys to their ankles/feet for some core strengthening with hands to feet 🧡Sitting: hold your baby at their thighs so they can engage their core and practice reaching up for toys. This strengthens their extensor muscles in the back while engaging the core for balance