Lava Dome was good, the tour was ok , the guide told too much, the kids were not so enthusiastic.

The Geysir Museum is much too static and sterile for me, nice and chic and not even something to eat except sugar stuff and cake on offer.
The museum was certainly a waste of money.
The ride to the geyser was delayed by 15 min, so you had to step on the gas on site. The geyser itself is basically fake, so more of a show than anything else and so it looks on site.