Yes, lavender is one of the most difficult things to start from seed and probably not a good choice for working with a four year old, because results will be so far off.
To start with, it benefits from cold stratifying. That is you put your seed on moist potting soil (just press it lightly so it is in good contact with the soil and don't cover). Sprinkle it lightly with water, then wrap the whole thing, pot and all, in plastic wrap and put it in the 'frigerator for three weeks. Then bring it out, put the planter on a heat mat to warm the soil and put lights directly over it just a few inches away. The lavender seed needs heat and light to germinate. And you have to keep it damp but not wet for up to three more weeks with the heat and light before it germinates.
Then you will have a few little seedlings that will continue to need careful care for a long time. In my climate, starting lavender indoors in February, planting it outdoors in May, by fall the seedlings may be 6" tall. Then it goes dormant in my winter and in the second year turns in to a real plant. In my climate, lavender doesn't bloom the first year from seed. Possibly it might for you, depending on where in NV you are.
There are plenty of flowers that are a lot easier and more rewarding to start from seed!