The park doesn't offer an extensive system of trails. I finished the only trail in less than an hour and I was moving fairly slowly. The terrain is pretty mild, with a few gentle slopes. The snow was pretty hard-packed this afternoon, which made the short downhill sections a bit more challenging. With fresh snow, it would be very accessible for beginners.
Despite being closed to motor vehicles, the reserve had been used extensively by snowmobiles. They had packed the main trail pretty solidly and they had gone off-trail frequently.
If Eliason's one trail isn't enough, it's a short walk to Bishop's Bog. I did that and extended my outing by another hour. West Lake would be another option, with just a bit longer of a connecting walk.
Eliason Nature Reserve
9202 Portage Industrial Drive
Portage, MI 49024
[address is approximate]