An basic iPad/iPhone could work well - even when he was too young to unlock and use it much, my son was able to voice dial with 'Hey Siri, call Dad on Facetime'

An basic iPad/iPhone could work well - even when he was too young to unlock and use it much, my son was able to voice dial with 'Hey Siri, call Dad on Facetime' etc, and it was easy to make it to work from the lock screen. He didn't even need to touch it - turning on auto answer in the accessibility settings helped too.