For the kid thing in Southcentral, what works for my GC's (now 10, 7, and 3):
- As mentioned, Seward Sealife Center
- The Quartz Creek/Cooper Landing areas: several places to hike if you want, but as Tonymull mentioned, also places to see salmon and possibly bears.
- From Cooper Landing, there several boat trips available....ranging from serious salmon fishing to not-so-serious trout fishing to essentially sightseeing.
- If you're in Homer, the trip across to Halibut Cove is nice...and (for Mom/Dad) apparently, the thing for all visitors to do is to get a t-shirt that says you visited the Salty Dawg.....which IMNSHO is what most folks outside of Alaska would call a dive bar, but to each their own....and I haven't been there for 10 years or more.
- If the focus is on the kids, I'd strongly suggest Kepler Lakes just outside of Palmer. Rent a couple of canoes, catch a few small tame trout, great kid stuff.
- Eklutna Lake is nice enough. If the intent is to take half-a day or so, that would be great. If you're simply looking to breakup the leg from Denali - Peninsula, I'd suggest an extended stop in Anchorage. The Museum has a kid learning section called the "Imaginarium" that is always a surefire hit for kids from 2 - 12. There is also the Eagle River Nature Center (or a name close to that).. essentially a low-key visitor center at the Eagle River entrance to Chugach State Park. Some displays of animals, etc, some observation areas, and a wide variety of hikes if you want to do that.
- I'd also recommend the "Alaska Zoo" on O'Malley Road in Anchorage. Won't compete with any zoo in the L48, but has lots of Alaska Wildlife and offers up close views for the kiddos.
- Wildlife Center in Portage would be a good diversion, it's become more touristy as it has expanded, but that's not all bad.
I'd still suggest either going North or South and that doing both will be a challenge....but any trip to Alaska will be enjoyable.