1. Mid grade should be fine if you keep the contact light. If you're going full speed, full strength, then get heavy grade. I wouldn't recommend trying to go all out so quickly in your marriage.

You could also get a couple extra blades, just in case.
2. The sales are pretty frequent, but you never know what will be up for sale it how much of a discount you'll get. If it works for you, then you should probably take advantage of it.
3. There is a noticeable difference between tri cree and standard, but it's not a huge difference. Even the standard bulbs are plenty bright. I'd go with colors you like as opposed to only going with a tri cree color you don't like as much just because it's a little bit brighter.
4. I'd get her a 32 inch blade.
5. If you're getting sound, go with premium sound (v4 is well worth the price difference between that and v3). The lite soundboard uses standard batteries, and those have a tendency to come loose during duels. And, with the lithium ion batteries AND buck puck option, you get a brighter blade for the length of the battery life. This is super important of you get Sunrider's Destiny or purple. Otherwise, one color will dim faster, and your purple blade will end up looking pink or red, and your teal blade will look green.
Congratulations, and have a blast. If you have any more questions, feel free to ask.