What do our Baalei Mesorah suggest we do to engage the children in the Seder night?
Furthermore, how effective do you think those methods would be with children of today?
My Ba'al Mesorah (my Rav, R' Mordechai Friedman) would offer his children candy for every question that they could come up with. I don't know how well this would work with his children today, as they are mostly grown.
He used the example of a politician engaging a reporter at a press conference. The reporter asks a question that he has been itching to ask and finally has his chance, but the politician answers a totally different question, delivering his message as he sees fit. This message then gets printed and publicized. Why does this work? Because once a question has been asked, the asker is engaged and is listening for the answer. It can be any question - why do we eat only Matzah? Why do we eat only Marror? Why do we dip twice? Why do we lean? And the answer is, "We were slaves to Pharaoh in Egypt, and HaShem took us out....It happened that Rabbi Eli'ezer....R' El'azar ben Azaryah said, 'I am like a 70 year old man....'"
In other words, engagement is key to keeping a child's attention and teach them about our national story and our spiritual relationship with HaShem. You can keep them engaged by allowing their imaginations to flow freely, with some built in cues and some incentives, and then you can teach them what they need to learn.