Ya those planters for sure will work. Also if you have time you can make planters out of scrap pallets. I made a few last year with some I had left over. Drive by any new construction with brick facing, usually those pallets don't have a deposit and the contractors will be happy to toss them. I prefer to recycle when gardening, makes me feel all green and stuff, helps me offset the fact that I drive a 6.0l gas engine around
For buckets too, free is better than $3 a piece, painters, garden centers, landscapers usually have a pile laying around. But if you do end up buying them $60 will last you 5 solid seasons. I try to look at the long term investment, not the upfront cost... upfront my numbers are pushing $1000, for that much I could ship in a lifetime supply of hot sauce.
You can easily get 10 plants in a garden that is 16'x4' My first garden (pictured below) was tiny, I excavated 6" of soil under it, and filled up 1' of premium compost. It was on the West side of a house, and got a decent amount of sun, but I crammed the garden with: A bhut, a hab, 8 Roma Tomatoes, 2 Big Red Tomatoes, a 9' tall cherry tomato, 12 onions, 2 Jalapenos, 1 sweet bell pepper, 2 hot banana peppers, 1 zucchini, 1 cucumber (the zucchini and cucumber I let grow out of the garden they get massive, and a small patch of parsley and cilantro. A small garden can go a long way. I even planted late, and I am in Toronto so the season is short. I had enough salsa and veggies, and I was giving bags of tomatoes away. Planting nothing but peppers in a garden that size with ample space and light, your laughing. And the planters you have already have more sq/ft than mine... your golden man.