Need some advice on how to proceed.

My lovely, delightful niece (7) has been taking a musical theater class, and is having a recital on June 1. My SIL and brother asked me months ago if I'd like to go ("to her play" is how they phrased it), and of course I said yes. My mom generously bought the tickets for us.

As we get closer, I've now gotten the details. It was sold to me as a play; really it's a recital. As in, a dance recital (her class takes place at a dance studio). The performance is at 6pm an hour and a half away from my home. According to the recital line-up, she is the 23rd performance of the night and will be on stage for less than 5 minutes.

If it were just me going, I'd be totally up for it. Even if it were just DH and I. But we'd also be bringing our 2 year old DD. Whose bedtime is usually 7:30. Because when we said yes we thought the play would be at like, 4. We shouldn't have assumed, but also... niece is 7. We could technically get a sitter, but it would be the very first time she's had a sitter other than our parents, and no one has ever put her to bed other than me or DH.

I've already emailed my mom asking her if she'd be upset if DH stayed home with DD. I'm really hoping that she'll understand.

Separate, not-sure-if-relevant notes: I'm 6 months pregnant, and recital is on mine and DH's 5 year wedding anniversary.

What would you ladies do?