Lassen Volcanic Park has a lot to offer for everyone. The park has wide roads, and most tourist spots are easily accessible. Here’s what I would recommend
Subway cave Lava tubes - easy 1/3 mile underground hike
Hydrothermal Areas - Hydrothermal areas from where Sulpher escapes regularly. Some right next to the road and some accessible via a short hike.
Walk and play on snow-covered areas - all along the park
Strenuous hikes
There are three strenuous hikes. I would only recommend one or two of these
Lassen Peak - this one is snow-covered almost year-round
Cinder Cone Nature Trail - This one is less strenuous compared to the other two. It is still hard due to the gravel-covered surface Cinder Cone seen from the bottom
Brokeoff Mountain Trail - this can be snow-covered hike depending on the time of the year