I too have found that structured activities help a lot when new babys are around. Art and craft is an easy way to engage the children and you can be holding baby at the same time.
All of mine have had reflux and I found wearing them in a sling a god send. Baby is happy and upright helps, you can use your arms and get stuff done.

I too say I can't understand them if they are whining or shouting. But I find if they are doing it a lot they are in need of some extra cuddles.

Its a big time for you all