Having studied the book, you have some idea of what each Tarokka result can entail, and you can let this "foreknowledge" inform Madam Eva's reactions to the cards as they appear. If you draw

the 7 of Coins, you can hint that the location of the treasure isn't very far away; if you draw the 9 of Coins, Madam Eva might shake her head despondently and say "Maybe save this one for last."

It's easy to want to add merely emotional clues, to add color without giving too much away: "It is in a place of dread;" "I feel the presence of mournful spirits near this item;" "This place is cold and silent." But there's so little emotional contrast in Barovia that sentences like these can easily fade into the background noise of doom and gloom. Specific information will make your players' ears perk up, and if your goal is to create a memorable experience, you can afford to drop a few extra hints.

For example: Many of the speeches for cards that clue

locations in Castle Ravenloft don't actually refer to the castle ("We know it's in a crypt. Do we know where a crypt is?"), but Eva can add something about "beneath the Devil's tower" or glance nervously in its direction.

If the players feel like gabbing it up with Madam Eva about each card, trying to pry hints out of her, go ahead and respond according to the character you've built in your performance—but to add emotional texture to the scene, make her insist on total silence before she turns over the next card.

The use of a real deck is so effective because everyone loves props. The description of Madam Eva's tent provides a lot of inspiration for additional props: Mysterious lights, a crystal ball, and a black velvet cloth. I think this cloth is a good thing to focus on because you can slowly unroll it before you lay the cards down, which is a very evocative and almost ritualistic action. Even if your players forget what cards you drew, they will remember the appearance of that cloth unrolling across the table.

If you can't get a piece of black velvet, use whatever spooky-looking fabric you can get your hands on, and then change the words "black velvet" to whatever you're using when you read the description, so that the players will think you are following the details in the book exactly.

(On the subject of

Strahd's Enemy: Some of the results are more interesting than others. The book gives you the choice between NPC A and NPC B for some results, apparently according to what kind of Challenge Rating you want for the party's ally. Obviously you want to figure out your choices in this regard ahead of time. But for my purposes, I didn't really want my players to end up with either version of the Broken One, the Horseman, or the Innocent, so I just removed those cards from the deck. If you're not comfortable with the full range of randomness in the book, you can create "massaged randomness" without the players finding out.)

I recently finished a CoS campaign with a small, somewhat oddly-built party. As a module, Curse of Strahd does a pretty good job of keeping the pressure on with very little work from the DM. It's fairly easy to tweak encounters, although as a warning it is also not too hard for the PCs to wander off-track and bite off more than they can chew!

Aarakocra and Flying Players

For your specific example, I think Barovia is a fairly safe place to have a player be an Aarakocra. There are a lot of things you can bring in to make things easier.

Terrain

A lot of the valley is forested, and the forests are described as incredibly dense, twisted, dark, and foggy. Flying in there would likely be difficult if not impossible.

The forests are also, like everything else in the valley, an extension of Strahd's will: if it's narratively useful for the trees to claw our Birdman from the sky, they could.

As a side portion of terrain, there are a lot of indoor scenes where flying wouldn't put you meaningfully out of reach.

Enemies

Flying may not put you out of reach of your foes here. While some humanoids might not have a ranged weapon it would be easy enough to add one, and additionally, this is gothic horror with a vampire baddie. There are quite literally endless bats.

Perhaps more dangerously, Strahd and Bucephalus can fly as well.

There is also the Roc of Mount Ghakis, which I had planned to have chase any PC that got too high up. I viewed this "Fly too high, attract the big fish" mechanic as a way to prevent reprisal-free fireballs from 200' by a flying sorcerer.

Weather

Barovia's weather is miserable. It's always overcast, often rainy, and storms are common. Flying in a rainy windstorm sounds like a great way to let the DM move you every turn. Lightning is a very real thing that I'd totally have intersect with a 150 lb chainmail-wearing bird on its way to the ground.

But really, the number one in my mind is: unless this is formal AL play (since they ban L1 Aarakocra anyways), don't worry about it too much! As this excellent answer on flying PCs explains, it is often a self-limiting feature that you as the DM should be aware of, but not worried about.

General Class Balance

I had a party of largely Unearthed Arcana multiclasses, and found it balanced out pretty well. Honestly, for a group going into a campaign with a known vampire big bad in it, they went pretty light on the Divine magic.

With one exception (see spoiler), I didn't see any combo in-game or during spitballing sessions with my players that would seriously de-fang anything in the game. Be sure to pay attention to action economy and estimated encounter difficulty, and you should be fine.

The one exception: Strahd himself. The climactic fight is written to be largely party-vs-Strahd. He's relatively tough and hits hard, but he's losing in action economy and the Sunsword will remove a lot of powers and cause him serious harm.

I found you need to play him very carefully and very smart. But remember: he's a master strategist and has been spying on the party via his animal and human servants, and with Scry.