Good question for the GW fruit forum.

You can graft. You can try from seed, it should come true if you plant more than 4 IIRC (may be 8). You can also air layer (kits available via several catalogues). You can try cuttings, may work if you're lucky. I'm going out tomorrow to air layer a ~100 y.o. apple and 2 pears of similar age.

Dan

marg,
If you bud/graft from a Macintosh, onto one of these established trees, whatever grows from the bud/scion that you put on will be 'Macintosh', but it will have no effect on the rest of the tree.
Grafting is easy and fun! Apples & pears are among the easiest things to graft, and are very forgiving of less than perfect alignment.
We sometimes joke that - especially with pears - if you just throw the scions at the rootstock - or, just get them together in the same room - you'll be successful.
Rooting/air-layering will be hit-or-miss(with probably more misses than hits), but might be worth a try.
Grafting/budding is probably the most successful and quickest method of cloning any of these trees, if they're desirable - select a rootstock type suited for your soil and growing conditions(ultimately YOU are in control of how big they become, so don't count on a rootstock to do that - they don't just stop growing once they reach 4-8-12 ft.)
Apple seedlings will be quite variable; nothing I've ever seen in print to suggest that they come anything like 'true' from seed. Stonefruits, yes, but pomefruits, no.

Everything Lucky said plus...

The success of rooting a cutting or air-layering depends a lot on the apple cultivar (or on your individual tree if it's a seed-grown tree). Some cultivars are relatively easy to air-layer. Others appear to be more difficult or even impossible with traditional methods (i.e. no one has claimed success yet). Rooting cuttings is, in some ways, similar to air-layering but more difficult (less likely to be successful).

The "seedlings" really close to the tree might be root suckers.

Although Lucky is 100% right about the rootstocks not really limiting the ultimate size of the tree, more dwarfing rootstocks do slow growth and make keeping the tree small MUCH easier.

I wonder just how old these trees are. Have you any clue? They may not as heirloom as you suspect and you may be able to find out the variety with some simple investigating and not even have a need to try to propagate them and find them easily available in the trade. I live on a farm on which I know for a fact had an orchard in existance since at least 1835, because it's plotted on a map where some apple trees still remain. I'm assuming they are wild progeny from when the orchard was actually cranking.

Sounds to me like there is some doubt the fruit may be a good quality, even in a well-tended situation with a young tree. IOW it's an unknown. So are you wanting them for mostly ornamental purposes?