Activities for our four month olds

Our babies will be going on four months this month! Graduating from the newborn stage ready to explore the world. My daughter loves to be held she'll have a fit if we put her down but I'm at SAHM mom of 6 including identical twin boys I have my hands full. I'm looking into activities for my baby that won't have her lying on her back so much, she has a bald spot 🙁 A friend of mine recommended a jumper I thought it was odd given her age but I read the reviews on a few and decided not to buy one. Any suggestions?