How can I make a raised garden that's kid friendly and under $150?

The easiest way to make a raised garden is simply by building a 4-sided box. Use four pieces of lumber (have your local building center cut them if needed), and screw them together on the ends to make a box that fits your space. Lay two layers of cardboard in the bottom of the box to help prevent weeds, then layer soil, mulch, etc for the plants you choose. A long narrow bed might be easier for children to reach into...and some plants that would be fun for kids might include things like cherry tomatoes, lettuces (fast growing), cucumbers or even green beans that be grown on a small trellis. Make it fun, let them help with watering and weeding....They are more likely to eat veggies when they have helped grow them!

buy a child wagon and drill some holes in the bottom for drainage....kids can move their garden, protect their garden in the garage during storms, stow the wagon in winter, take it to grandmas when they visit so it gets cared for while they are there...easy to maintain- no moles, grub worms, ants, can be moved for sun or shade....just big enough to keep kids happy and small enough for short attention spans

You could also use a flower pot their height. Let them fill half with aluminum cans then soil. Now plant you plants. You can also start a bean seedling by put a damp paper towel and a bean flat in a ziplock.

you can check it everyday until has roots

You could use styrofoam peanuts 🥜 in the bottom of pot to make it lighter. Crushed plastc bottles work also.