Design ideas or what to do with it differently than my plan also welcome…

Get it powder coated. Powder coating will not peel.

How should I treat it before powder coating ? Which product do you recommend?

If the only place that you have available to work on them is your balcony, I don't think you could attempt powder coating. It seems pretty messy and involves special equipment, I think.

I was going to suggest taking them to an autobody shop to have them sandblasted and perhaps painted.

If you want to DIY, then get a wire brush and steel wool to clean the old finish off (and protective eyewear, mask and gloves!) plus a tarp to work over. Ask at your local paint store what paint is most suitable to use.

Rustoleum spray paint.

https://joyfulderivatives.com/patio-furniture-refresh/

If you powder coat them you have to take them to a place that does it. It's a much harder finish than spray paint and will not peel. Taking them to an autobody shop is a great idea also. I had a table and 4 chairs powder coated a few years back and it cost me $600 and that was the family discount from my brother in law. He did it at his place of employment. It's not cheap but it came out beautiful. No more spray painting for me.

Powder coating is preferred , but pricey and you can’t do it yourself. I’ve painted my wrought iron furniture many times over the years and found spray painting is easiest, but doesn’t last. A rustoleum paint applied with a brush lasts longer.

Rustoleum website has lots of how-to and pics. YOu might want to strip off the paint esp where its rough. If your balcony is somewhat protected, and if they can be well covered in off season theyll be fine. So amaybe you retouch now and then.. How old are those - very cute, a metal version of rattan. What fun! What color?