L.B.
Your wind down process may be too interesting & may be causing him more excitement. My youngest loved school & had trouble going off to sleep on her own. Reading her books & singing songs was too stimulating. We learned to bore her to sleep. Here's what worked for us: avoiding any stimulants like sugar & of course caffiene, darkening the room as much as possible, making sure no sounds were distracting her (like TV on in another room) and humming a simple tune over & over.