Here are some suggestions to help with those "young" hands:
For younger children --
Serve meals requiring the use of silver instead of finger foods to help children develop a proper hand grip.
Provide a fun activity that uses the hands such as cutting pie dough, pizza, or Pla-Doh
with a pizza cutter or cookie cutters.
Use modeling clay to mold creations instead of Pla-Doh. Those muscles must work much harder with the old-fashion type of clay. (Watch your carpet though.)
Spell out letters with clay.
Practice letter formation with instant pudding on a cooky sheet. (No clean-up)
Practice writing with the fat markers on old newspaper. Make the letters as large as possible. (Always use the correct path formation.) Then put some smaller letters on the inside.
Cut with child-size scissors. (Supervision needed)
Play on the monkey bars at the park. Strengthen those shoulder muscles!
For older children --
Encourage outdoor sports using hands. Play catch with a large ball; move to a smaller
ball as skill improves.
Teach simple childhood games such as jacks or marbles.
Often children with poor muscle strength and low endurance cannot sustain the required level of written work despite high intelligence.
Provide a computer and simple software programs for homework and creative writing.
Encourage writing letters to grandparents or penpals using the computer.
(Thanks to the American Occupational Therapists Association for some suggestions.)