Flying with 18 month old

L

Any and all tips please! We have a round trip flight coming up in March (2 1/2 hours each way) when my daughter will be 18 months old. For those of you who have purchased a seat for your toddler, did you use one of those CARES FAA approved harnesses? Did you just hold them on your lap during takeoff and landing? This is a US flight with Delta if that's relevant btw. I have so much anxiety as I rarely ever fly and this will be the first one for our daughter! Luckily my husband will be with us. She definitely doesn't like to sit still so any tips on keeping her busy for the duration of the flight would be appreciated. Thank you in advance! ♡