Making art at the Tate Modern.

Most museums here in London are free, and this rules for at least two big reasons.

First: It makes sightseeing cheaper.

Second, during those inevitable moments when your kids act like kids and you need to pull anchor and abort the mission, you don’t have to worry about wasting money.

I’ve come to appreciate the first reason slowly over the 40 days we’ve been here.

As for the second lesson, let’s just say I had a crash-course in learning that one on Thursday, when I took the girls to the Tate Modern museum of contemporary art to celebrate L’s first “Exploration Day.” (For more on the back story that prompted these special weekly adventures, click here.)

The trip started fine. After an uneventful Tube ride to Southwark and a seemingly interminable walk to the museum, the kids climbed on a stair sculpture out front, then excitedly proceeded to the galleries. We hit the brand new Bloomberg Connects bar first, so the girls could ease into the experience with some interactive e-drawing (the units themselves mimicked drawing on a tablet computer, only the pictures posted to a giant wall).

Because the drawing went so well, I thought I might try to expose them to some of the actual art.

This, however, is where the day went south; as we walked through room after room of paintings and pieces in various media, the kids lost it. Big time. They started rebelling with yoga on the floor. Then they hopped around, belting a song from “Doc McStuffins.” In the middle of a crowded gallery.

Finally, when R quite literally ran over and climbed up on one of the art pieces, it was time to go. So we hit the café. Then we went home.

All told, we spent about 90 minutes at the Tate—40 minutes with the interactive e-drawing, 40 at lunch and about 10 minutes in the galleries. If I had paid full-price for that, I would have felt gipped. But because everything but our fish-and-chips lunch (natch) was free, it was no big deal.

I know the thinking behind free museums is to make them available for everyone, but I think the approach benefits (adventuresome) family travelers most. You know the saying about how to roll “if at first you don’t succeed,” right? Let’s just say I’m thankful that we have another three months to get back out there and try, try, try again.

How do you determine when it’s time to abort a travel mission with your kids?