Altocumulus and Macmyday are both more well-traveled than I am and so they have a better perspective than I do regarding Iniala, but I just thought I'd add a few things to consider.
congrats on the honeymoon. It may depend on your personality. The tented camp is a lot of fun and when we went there were two other couples that were also on their honeymoon, so if you enjoy socializing you'll be able to share drinks every night, and how that might balance with your time down south.
We've only stayed at four different Amans, and with the exception of Amankora, people really seemed like they wanted to keep to themselves, and frankly it felt weird sharing a hotel with people who wanted so much privacy. If you prefer to socialize I would probably go somewhere like Point Yamu. FWIW: I have only been to Iniala and Phuket and can't speak from experience unlike other posters on here.
One more thing to consider is activities. At Iniala we had a driver who took us on any whim to places like zip lining, monkey shows, shopping, Tiger visiting, etc... plus, you'll no doubt want to take a boat out to the islands. Iniala set that up and we only paid "cost" whereas I heard that Amanpuri charges a significant markup. They both use the same boats, from the same owner, who I walked past when we were at the marina. Plus the BBQ-- a $500-$1000 charge elsewhere.
For children, no doubt, Iniala is superb. Though I liked the Siam villa more than the Penthouse.
One other option would be to rent a villa. Luxury Retreats markets a lot of nice places.