Almost all apples and crab apples can pollinate each other, so as long as you have different kinds, I wouldn't worry about it. Crabapples are particularly good pollinators because they bloom for a long time.

More importantly, what kinds are you planting exactly? When you say you've started some trees, do you mean from seed? Apple seedlings are very variable. They'll resemble their parents only as much as, say, we resemble our own parents. And if you don't know who the father (pollen parent) was, it's even harder to predict what the offspring will be like. What if that tasty light red apple of yours was pollinated by a tiny sour crabapple? If I were you, I'd make sure I knew exactly what I was planting, and buy some grafted trees.

Then again, it can be fun to be surprised, so if you like surprises, enjoy.

"What if that tasty light red apple of yours was pollinated by a tiny sour crabapple?"

If that tasty red apple was pollinated by a sour crabapple, the apples would still taste like those tasty red apples. Only the seeds would contain the new genetic material, and you aren't going to eat those seeds. Now, if you planted those seeds and grew more trees from them, THEN you would be gambling on what that second generation of apples would taste like.

The fruit of any plant successfully pollinated by another will be like it's parent.