seeds saplings sources & suppliers

Hello, maybe you could give me some tips on choice of tree, and where i can buy seeds.

I need to plant 4 or 5 (cherry) trees for a garden that will be enjoyed by children. so the requirements are quite simple...
large blossoms, different colours,
no poisons in fruit, flowers, bark, etc.
no bad smells (apparently some smell bad)

After reading lots, and getting myself more confused than before i started, i've come up with a shortlist of

CHERRY-------------
Shogetsu (white), Kanzan (pink), Ukon (yellow), or
Japanese mountain cherry - Prunus serrulata
Yoshino cherry - Prunus x yedoensis
Prunus serrula

WILLOW-------------
Salix babylonica L. - Chinese Willow (dry areas)
Salix lutea

So if anyone has any tips, please let me know, regards, Jon

just off the top of my head - why not also plant a few traditional fruit, cherry trees, in addition to the other trees, the fruit trees have beautiful blossoms and bear yummy fruit. The children would love to climb up and pick the fruit - like I did and still do! so much fun. I'm assuming you have space, judging by the list of trees you have come up with...