My partner and I will be driving from Enns to Hallstatt on a Sunday morning in June.

We will spend the night and then on to Salzburg.

My concern is that the tourist office will be closed on Sunday and we won’t have much to do.

How about a small boat rental or hike?

Chances are pretty good that the tourist office will be open at least part of Sunday.

Poking around town is fun.

Taking a row boat out is another option. Also, there is a funicular going up one of the mountains. You may want to walk down from the top. There are many other walks and hikes around the lakes and into the mountains. Unless it pours rain, you won't get bored if you set your mind to it (and your energy holds out).

Almost everything is open for at least part of the day on Sunday so Treplow is right, there is plenty to do. You might also check out the wonderful Hallstatt Museum. We thoroughly enjoyed all the wonderful exhibits and they will give you info in English if you ask when you buy your ticket.

My plan is to spend the night, do you think it will be a good idea?

Not much of a night life, so you have to decide.

not much to do at night, but waking up to that scenery when the dawn is just breaking is something I'll never forget

Have any of you rented a small electric boat or taken a boat tour? I am having problems finding a site for schedules.

Since many visitors to Hallstatt are "daytrippers" the town is much calmer in the early morning and evening so you can get a better feel for the place if you stay overnight.

I was able to find the site for boat trips from Hallstatt. Unfortunately the tourist information office may be closed on a Sunday.

I just posted a reply to a question about Salzkammergut. If you search for that word in the bar above, you'll see the reply. The ice caves may be open for tours on Sunday. They are outside of the town, near Obertraun. You need to hike for quite a way from the bus which takes you up, then go down into the caves. Wear warm clothing. Some of the local museums may be open also. I think there is a cable car which takes you up for a view from somewhere in the downtown area.