Epsom salts is great stuff, but I'd be careful of adding it to the soil mix, Linda. Better to add it to the soluble fertilizer you'll need to water them with after transplanting. About a tablespoon per gallon is a good amount to start with.
Bark nuggets from mulch are pretty big, better to use something a bit finer, I think. The 50 percent manure might be a little bit rich for small plants as well. Manure releases an initial rush of nitrogen fairly fast once you are watering regularly. Any chance you have access to alfalfa pellets? It's horse food that hasn't gone through the horse yet, so without all the urea compounds that make manure so high in soluble N. The pellets are available at a feed store or Tractor Supply for about $15 for a 50lb. bag. It will last you all season.
Are you planting in the ground or in pots, Linda?