Have your kids place the pellets in a plastic tray. The one in this photo is a smaller propagation dome that holds 12 pellets. It costs $1.99 at Home Depot and comes with the 12 pellets. Since I have had this one for a few years I needed to buy the replacement pellets as shown in the previous step. My 2 year old and 4 year old enjoyed putting the pellets in the tray.
Using a plastic cup, fill with warm water...not hot and not cold ... WARM water. While the pellets will expand on hot water, it does not make for a great environment for the seeds. Cold water will "eventually" get the seed pellets to expand ... do you have an hour or so? Warm water will make them expand instantaneously.
Here are what the pellets look like once they have expanded.
Have your kids choose something they would like to grow. In my son's case, here we are planting broccoli. What can I say, I am lucky, the young man loves to eat broccoli, so growing it makes perfect sense.
Just remember the smaller the seeds you choose the more likely your child will pick up A LOT of them at once and plant a bunch in each pellet. It's not really a big deal, you will have to go back later after they sprout to thin each pellet out. Once they reach the top of the dome, carefully use a pair of scissors and snip the extras leaving 1 or 2 plants behind. Using larger seeds makes this easier (i.e. squash, watermelon etc.).
Have your child put the dome on top. This helps seal in the moisture and create a greenhouse. A constant temperature and moisture level will exist, making for a perfect seed starting environment. If you are using your own home made tray you can cover with clear plastic wrap and that will serve the same purpose.
Place the finalized tray with pellets, seeds and dome on a window sill that receives sunlight first thing in the morning. For faster germination, place it on the same window sill NEAR (NOT ON) a heater vent.
CAUTION: NEVER PUT IT ON THE HEATER VENT!
And that's it! Your seeds should germinate in 5 to 7 days, probably sooner. Once they grow tall enough to where they can no longer fit under the dome, I like to plant them in their own individual pots, if the outdoor temps are not ready for transplanting.