Which hotels have indoor waterparks and are nice this time of year and suitable for a 1 year old? What other attractions are open this time of year?

try Great Wolf:
http://www.greatwolf.com/dells/waterpark
http://www.wisdells.com/ to find out what's open. Obviously waterparks are a no and boat rides may shut down about this time here in mid October....there's still places out and about the town, shops included that will be open and running.
http://wisdeerpark.com/ through Late October. We loved it here.
http://www.randgn.com/ Riverside and Great Northern Railway, nice short trip
This weekend is probably the last weekend for ANY seasonal outdoor -- if they are not closed already. Weather is turning cold.
Great Wolf is good for younger kids. Kalahari recently remodeled their indoor waterpark kiddie area -- and they are the most likely to be open normal hours. Folks often complain that Great Wolf has very short hours during off season. If you want less fancy and less money, consider Polynesian.
I agree with hatchpal4u
"http://www.wisdells.com/ to find out what's open. Obviously waterparks are a no and boat rides may shut down about this time here in mid October....there's still places out and about the town, shops included that will be open and running."
http://www.wisdells.com is a great place to start looking.