SihanoukVille can be a great place for kids to visit.
Beach most of the day, sightseeing trips, island adventures, boating, rides in a tuk tuk (cart pulled by a motorcycle), swimming in the pool, playgrounds,
and a good night's rest after a long day.
SihanoukVille is not a great place to leave your children alone, (though there are over 80,000 children under 15 years old living here)
The most dangerous place is walking along the street, where the traffic rules are much different than in your country. Guaranteed.
Several of the hotels have swimming pools (SihanoukVilleBeachResorts.com), many of the hotels and guesthouses are right on the beach (mainland and island beaches), public playgrounds are hard to find, but several hotels and fast food places have them.
Food shouldn't be too much of a problem, as if they don't like the local food, there's over 250 restaurants serving foreign foods from all over the world, and over 800 restaurants have Western food (think burgers, pizza, sandwiches).
Medicines, we have a lot here, but not such great medical facilities.
Day care (for foreign children) is hard to find as well.
Some specific places and activities for children are.....
* The Big House, a zoo and restaurant near Victory Beach.
* A trip to the islands.
* A day at Sokha or Independence Hotel. There's a fee for using their facilities if you're not staying there, but it's fun.
* Beach. Any of them or all of them.
* A walk around the Central Market downtown. Not like your hometown shopping mall.
* A ride in a tuk tuk around town (or out of town in the countryside)
* Scuba diving class (obviously for older kids)
* A day trip to Ream National Park, (and a stop by the Kbal Chhay waterfall on the way back)