Advice Needed - Going Planted

Hi Guys, I would like your opinion on something I am thinking about doing. I was hoping some of you plant people might be able to help me make up my mind.

After successfully keeping the Vals I recently purchased alive (not a big achievement I hear you say but the only previous success I had was keeping algae alive!) I want to go down the planted route.

My issue is that I have small sized gravel in the tank to a depth of only an inch or so. I am considering two options for the tank

1) Leave as is and use fertiliser tablets/balls in the substrate. My concern with this is the depth of my substrate. I know some of these balls like JBL The 7 Balls are quite large. Is my substrate deep enough to keep the balls/tablets and plants in or will they suffer over time? Most planted tanks I see have deeper substrates than this. I would worry that my corys may move some substrate to reveal the tablets/balls.

2) I was thinking of temporarily removing the water/fish/substrate and adding a fertilised substrate such as Dennerle DeponitMix Professional Substrate, TetraPlant Complete Substrate or JBL AquaBasis plus and then putting the existing substrate back over the top (the existing substrate is a dark colour and I think it looks great). My worry with these is will I be able to put the fish back in straight away or do these substrates release ammonia, nitrate or anything else into the water? The fish will be in a 60L bucket while I am changing the substrate so don't want to leave them there for too long. I think long term this is the best idea, but seeing as how the tank is up and running it may be risky.

The plants I am planning to use initially are plants like Echinodorus 'Ozelot', Cryptocoryne Wendtii 'brown', Ludwigia repens 'Rubin', Limnophila sessiliflora, and in the foreground I am looking at Marsilea Hirsuta. Open to suggestions on other plants to use, my knowledge is fairly scarce on aquatic plants.

I will be doing a DIY CO2 set up, and have a Tropica liquid fertiliser (can't remember which one off hand).

Could anyone advise what way they think would be the best way to go? Really want to give this a go, have an image in my head the way I want it to look, so want to give it the best chance to work out well.

The tank is a Fluval Osaka 155L.

Thanks
Bill