If they are inside, I'd use roasted tomatoes. Roast them while you are making coffee or use leftovers from dinners from up to several days before. Take them out right when you get into the kitchen and let them come to room temp. Accent with whichever fresh herbs you have on hand, if they aren't already on them. Barefoot has a good recipe to roast cherry tomatoes if you need it.

I usually cut them in half, squeeze each half a little to get some of the watery bits out, then quickly cook them a little to release the moisture and guarantee that they don't make the egg watery. Plus, I really love the taste of fried tomatoes which you just don't get if you toss them in without cooking first.

It depends how you like them. I like them to largely maintain their shape and keep more of the juices, so I add them while cooking (though watch out because, when you bite into them, the juices will be lovely and hot). If you aren't fussed about recognising them as cherry tomatoes and want the juices to permeate the egg mix more thoroughly, then pre-cook them (and make sure you put all the juices, not just the flesh, into your omelette mix).

i would saute them a little bit first to release some of the moisture and prevent your omelette from becoming too watery. sauteed with a little garlic and olive oil would be delish!