I need to fly 4 people R/T from IAH to Paris sometime in late May or June and desperately need help cobbling together an itinerary that meets our needs and most efficiently uses our miles/plus points/future flight credits to get us what we want/maximize our chances of upgrades while minimizing our out of pocket costs to the extent possible. Being flexible on our dates is a blessing, but also a curse because it's made booking incredibly frustrating. Any and all advice welcome, but I will seriously pay someone to figure this out for me. Here's our requirements:

Dates: Depart after May 27th, return by July 5th
No of nights: 6 or 7
Status: I'm a plat (will be after a quick mileage run tomorrow), no one else in my party has status
Cabin: Ideally all 4 of us would make it upfront on the outbound, but we'll take what we can get which might mean 2 of us up there with the other 2 guaranteed in Prem Plus. Worst case scenario is we're all guaranteed in PP and some or all of us are waitlisted. I've accepted that the best we'll be able to do on the return is PP for all 4 of us.
# of miles: One of us has 120k, the other has 45k (sure wishing we hadn't burned all those miles this year!!)
# of Plus Points: 40 (after tomorrow sometime). My uncle is a GS and always gave us GPU's back in the day. He has a boatload of Plus Points we could use, if needed, once we've maxed out the miles/points we have.
Future Flight Credit: $560
Max stops: 1 (both directions)
Weird preferences: I need our outbound overnight leg to leave after 6:00PM CST and be at least 9 hours. The 6:30 IAH to FRA is one option, as is the 8:30 to LHR, where we would then just grab a BA flight to Paris. The ORD to PAR flight leaves at the right time for us, but there's no PP cabin (at least on the dates I've looked at). For the return, I'm not picky about connecting airports (not willing to hours and hours more just to get it cheaper though) but am willing to hop over to LHR and fly out of there if it gets us what we want (I know it's a hairy airport, but LHR has a bunch of 45k mile Prem Plus fares).

So, what itinerary and combination of cash/points plus/miles and flight credits make this work for us and on what dates? I was serious about paying someone to do this for me, btw...