2 days in French Riviera

Not much time but choose from a day trip to Eze or Monaco or Nice. You can do 2 of those in one day everything is close together short bus or train ride. Nice has all kinds of museums but it may be enough to walk around the old town and climb to the castle where there are some great views depending on the weather

ok great, so day 1 Nice old town and castle
day 2 day trip to Monaco and stop in Eze?

also, i'm not tied to those, is there anything else you would recommend instead of those places??

Lucky you staying in Cap du Ferat! Make sure you visit both Villa Ephrussi and Villa Kerylos there.
Nice is wonderful. I would spend a full day there.
Then, if you have time, visit Monaco, half day will do for Royal Palace, Cathedral where Ptincess Grace and Prince Rainer are buried.

As people noted, you can combine Monaco and Eze together -- Eze will give you the views. Hit Nice in the morning to mid day -- the Cours Saleya market in Old Town is open from early and is a must. On Monday it is antiques/brocante and the rest of the week is flowers, fruit & veg. Walk around old town, grab an ice cream at Fenocchio, take the elevator up Castle Hill and then have lunch in the Old Town or on the beach (walk along the Promenade). Hit Place Massena as well (for the architecture, or hit the shopping if that appeals), then return to Villefranche or Cap Ferrat -- there you can go (as noted) to the Villa/Jardin or take the long walk.

The Rick Steves Provence & the French Riviera Guidebook ($21.99 on this very website) has loads of good detail both for the suggestions above and for those things not mentioned.

Two days isn't a lot so having Rick Steves' suggestions for how to string together the different things and efficiencies can really pay off.