I doubt that it's too late to plant anything you choose to plant. I've never planted tomato seed in the garden, nor have I heard of anyone doing this. If I were you I would go ahead and plant anything you wish to plant but I would transplant tomato plants instead of planting seed.
I think WAY too much emphasis is put on getting stuff out as early as possible. If you can remember next year plant a few things in early April then wait until early to mid May and duplicate your "early" plantings. Without much variance your "early" stuff won't beat your "late" stuff by more than a week or two and you don't run the risk of losing tender plants to some of those cold April nights.
Of course I'm speaking of warm season plants like, beans, tomatoes, squash,cucumbers etc. Cool season plants like potatoes, cabbage, onions etc. can be planted without much worry as early as mid March. My experience is in East Tennessee (foothills of the mountains) , so these dates could vary to some degree in other parts of the state.
I have planted sweet corn and beans as late as July for a late crop. They don't do as well as they do planted early season but still have plenty of time to mature.