Restarting Reaper's Rewards

I don't think there's any way to do what you want. 

You don't need seed packets to get lilies and cherries. They are readily available by harvesting wild plants. Lilies can be found in the neighborhood of Magnolia Blossom park in Willow Creek. A cherry tree can be found in the Parched Prospect neighborhood of Oasis Springs, near the playground. Make sure you spend enough time in the neighborhood for the plants to grow and reach maturity, and then be in that neighborhood before 5 a.m. to make them harvestable. You should be able to collect your harvest by 6 a.m. These are both Summer plants if you have Seasons, so make sure it's the right season.

You can use Dr. June's Weather Control Device to change the seasons if necessary. You'll find it in Outdoor Activities and it costs 1500. You could put one of them in Magnolia Blossom park, for free, if you don't want to spend your Sim's money on it. I think you'll need to upgrade it before it can be used for changing seasons.