DD1 has just turned 4. For her birthday DH made her a "garden" (something a bit like this but all one level - total volume is around 200L). Plan is to go out this weekend to get something to fill it with and some seeds to plant in it.
For large pots I tend to chuck in a mixture of soil based compost, a bit of water retaining gel and some slow release fertiliser - and possibly some manure as well. I suspect she's going to wind up with easy annuals, mainly flowers, maybe some veg (I'd like to try carrots in the hope she might then eat them...)
So does that mix sound about right? If not, what would you change it to? She's so excited about having her very own garden to play in I'd hate to get this wrong and set her up to fail before she even starts...