Award Flights with Paid Upgrade...for someone else?

Hello all, first time post here. Been browsing the forums for a while now, but I finally have a situation I dont think has already been discussed (but I could stand be corrected...)

Heres my issue: I want to book my brother and his fiance their honeymoon tickets using my miles. I've been accruing for a while now, and have a total of about 145,000. (Premier Silver this year for the first time too. I NEVER want to go back!)

To get them from DCA -> DEN -> PVR -> DCA in August would use 140,000 miles. Not a bad deal, price is somewhere around $1,770 right now. (Oddly, its the same number of miles if I exclude the first leg from DCA -> DEN. Anyone know why? Just cause its RT overall?)

I would love to upgrade them to first class. Theyre young, you know, not big fliers, and its their honeymoon! Once in a lifetime for them.

So what would be better:
1. Use all my miles to book their flights. Let them pay for the upgrades.
2. Let them pay for their flights (I'd use their credit card). I upgrade them using miles.

This is all assuming theres no issues with my booking the flight for them using my account.

Would love to hear your thoughts, experience, and input!

Thanks!!