depends what you call small…
age 4 & under.. personally i put them to sleep and give them a mock seder on their level on first day yom tov!
older than 4 – father should be leading seder on childrens level and saving lomdisher divrei torah for later by the meal when the kids have dropped off to sleep.. or save it for another pesach seuda or afternoon when kids are not around.
Seder is a time to connect with children.. not give them a boring & dry experience.
It goes without saying that ALL children AND adults should take a nice nap on erev pesach. YES it is possible.. with a little foresight & planning. (& reward!)
If a child wants to leave seder table for a little break to read or play a game.. i see no reason..
Lots of singing & acting out the stories will keep kids up.