I'm on a bit of a retro kick so I am going to recommend a ruger single six with the 22lr and 22mag cylinders. Also I like the MKII's with the 5 1/2" bull barrel. I think ruger made one called the MKII 4B that had a 4" bull barrel on it that looked like a neat little hiking gun. I saw one a few days back that took my fancy, it is a ruger single six in .32. It is built on the same frame as the single six 22 but it chambered for the .32 round. Very handy little gun I would think. I don't need one, but I want one. It would be more expenisve to shoot than the .22 but I would think it would be a lot of fun. In any case, if you are looking for an overbuilt gun made to last - I vote for ruger (company politics notwithstanding).
Sig/Hamerelli also makes a neat little .22 semi called the trailside if what I read is correct.
For a rifle I would recommend a bolt-action or single-shot .22 without a scope. The one I have seen that I like is the CZ-452. They go for about 200 bucks and seem like very nicely made rifles to my ignorant eye. I like to teach youngsters to shoot with a long gun long before moving to a pistol. A pistol is just to easy to inadvertantly point at yourself or someone else when you are young and still learning. A rifle makes the learning a bit easier. Also, in a rifle I do one round at a time with youngsters. This is for two reasons - one, for safety. Two - I want to instill a sense of "this is the only bullet I have to work with" in their minds. For very little shooters I recommend the "chipmunk", a kid sized 22 bolt action single shot with ghost ring sights. I got my son one for his fourth birthday and we spent a year talking about it and cleaning it and dry firing with snap caps before we went to shoot. We started with .22 shotshells and water balloons, then moved to 22 shorts and then on to LR's. Now he can hit pine cones at about 15 meters. I treat it as a very somber and serious outing and I believe he highly values the trust I am giving him by letting him shoot. We talk a lot more than we shoot and I always stand right behind him. It is a good way to teach about patience and control, and of course it is just cool to be able to go shooting with him for me.
So, if it was just for me to shoot, I would get a freedom arms .454 for plinking. But if young'uns are going to shoot too this is my take on it. Good luck and please let us know what you decide on.
Don't forget little eyes and ears for the shooters, you can find them at the larger sporting goods stores.
Jake