Worry more about how that ties into your roof. Leaks will ruin a house.

I can visually see your concern, but honestly, I think the high number of them, make up for the individual size. Because you have more than just 2 ...aka one on each outer corner, I think they are structurally fine. If you want to 'beef' them up at the base, you might do so with some landscaping tricks? Such as a nice shrub on each corner or some iron planters? or cement pots with attractive flowing green ferns spilling out from them? Certainly you could also do some faux stone or brick bases on the lower 3 feet of each of them, boxing them in? I say 3 feet, there is likely a rule on what the standard should be. I would look for some gray tone bricks or stone. ? If that is just not your look, than perhaps you would enjoy a porch railing either just on the opposite side, that is, the outer 'wall' of the new porch, or perhaps on both sides and just leaving an opening between the 3 center posts in front? A railing from the wood matching your posts would be gorgeous. Or you could do it with black painted vertical wrought iron, or a rail style with 3 horizontal lines from post to post, except for the gap at the front to the left and right of center..., or white painted to mimic a picket fence since you have white windows & entry door..... Than find you something pretty to place in front of each of the 3 center posts, that are missing the porch railing, such as that trimmed bush, miniature evergreen? or even a lantern/downlight mounted on each of the 3 porch posts to welcome guests in the twilight/evening.. And like Sophie, I hope your home roof does not have any problems with the addition of the structure. Keep us posted!