文法

副詞は様々な位置に置くことができますが、次のような感じになると思います:
①　◎　Children are not so easy to please nowadays as they were in the past.
②　△　Children are _nowadays_ not so easy to please as they were in the past.
➂　◎　Children _nowadays_ are not so easy to please as they were in the past.
④　◎　_Nowadays_ children are not so easy to please as they were in the past.

◎とか△は個人的な評価でして、英語ネイティブの方による評価はまた異なる可能性があります。