Mother in law watching my children for a week

So I'm not sure if I should cancel or if maybe I'm just letting my anxiety take over my thoughts but I asked my fiance's mother if she could possibly watch our children next year for our honeymoon. We will be gone for about a week and this will be the longest I have been away from my children so I'm already having major anxiety about it.

I originally asked if she could come and stay at our house (she lives 3 hours away) and we would plan our honeymoon around her schedule, whenever she could take a week off. She was SO excited and happy to do it which was great because she is really the only one I trust to have my kids that long. Anyway, she ended up texting me today asking if we could just drop the kids off with her at her house (I was ok with them being at her house instead if that's what she wanted)and then went on to tell me more plans she had...

She wants to take them a few hour away to her sister's, then a few more hours to Seattle where her mom is.

I would totally be fine with this, my 12 year old will have a blast but my 3 year old is a hand full and a runner. She gets over stimulated when there is to much going on. It just makes me nervous to even think about having her stay in a hotel all week on top of that having so much going on, she has never even stayed a night anywhere without me! Is my mother inlaw going to chase her around all week in the busy streets of Seattle??

What if there is an emergency? I'll be states away and my family will be on the other side of Washington!

I obviously can't tell her what and where she should be watching my kids when she is doing a HUGE favor for us, right?

Am I being to anxious about this? Or should I just cancel our honeymoon?

Still a year away and I'm already an anxious mess. What would you ladies do?