L.U.
The team probably should have talked about that before the last minute!!
If no one did then I would go ahead and do a thank you card and maybe a gift card to somewhere you think/know he would like.
Last year my husband volunteered and coached for my son's team. It was a 12 games, 2 practices a week, and 16 weeks of soccer total.
He got $50 gift card to the Cheesecake Factory, $10 to Jamba Juice, and $10 to an ice cream place.