Opinions on 3 hotels

These are 3 completely different hotels in completely different areas of Amsterdam, so it’s really difficult to make a meaningful comparison.
If you want to know about potential noise issues of the Sir Adam, I suggest you to read reviews. If guests were bombarded with loud constant noise, they will definitely write about it in their review. The ferry to and from the hotel runs frequently, pretty much every 5 to 10 minutes.
The Hotel Mercier is indeed very conveniently located, which explains (part of) the higher price. Only you can decide if you want to spend the extra money per night.

I've not stayed in any of those properties, but I would check the reviews on Booking.com as only people who have actually stayed at the property can leave a review. As DutchTraveler said, if any cite noise as a recurring issue I would possibly steer clear. Based only on location and access to tram lines, I'd probably pick the Mercier or Notting Hill.

I love taking a ferry. We took the ferry almost every day for rides outside of Amsterdam.

The question that comes to my mind is whether you are a "get up, get out, run through the plan for the day, return & call it a day" sort or if you are more an "out and back in" multiple times sort of traveller. We generally get out, do a bunch of stuff, return later to the hotel for a pre-dinner freshen up, and then are out again for dinner and some evening wandering, so being a bit away from the heart of town is no real issue. But I wouldn't want to be doing the ferry a half dozen times a day.

That is a good point/question, Tom R. I am definitely an out-and-about type. When we took our Granddaughter on trips when she was younger, we frequently went back to the hotel for some downtime. I haven't gone on a city trip with her for several years so I will need to give this some thought. My guess is that it will be out-and-about for the entire day, with ours rests in parks and lunch break.

How many nights? Mercier seems obviously far more convenient, but Sir Adam not so much hassle and looks like fun hotel.

We will be in Amsterdam 4 nights. Then off to Krakow. The convenience vs price is a real dilemma. Both Mercier and NottingHill look good. I guess I will look at it as a good decision for either of them ... just different advantages/disadvantages.

To me, and this is just me, I'm more okay with a more outlying hotel for a stay that is a little bit longer like yours. Two or three nights I tend to want to be as extra convenient as possible. For four nights though sometimes it feels good to be a little out of the center.

You're right that there's really no bad choice. It's all fun! And it's really cool that you're traveling with your granddaughter, so special. Have an amazing trip! :)