Try digging the Japanese maple seedlings up when not in leaf and planting them where you want them.

The second picture shows a 'Kanzan' ('Kwanzan') Japanese flowering cherry. The last is a common lilac (Syringa vulgaris) cultivar. There are many of these, perhaps someone else has an idea which particular one it might be.

I would go ahead and transplant the maple seedlings now, being careful not to damage the roots. Put them in small containers with good quality potting soil, and keep them in a shady location. Make sure to keep them watered through the summer because small pots can dry out quickly. Trees get hard and harder to transplant the larger they get, so that's why I recommend doing it now. Winter or early spring before leafing out would be better, but you probably wouldn't have noticed them at that time.

Thanks for the replies. I could put fencing around the small seedlings and wait for winter before transplanting if that would be better. I think I will do a combo of the two ideas- transplant some now and mark the others so I will be able to find them in the winter to transplant the rest. Thank you also for the I'd s on the tree and the lilac.