Hi! I'm going to WDW in February CL with the extra FPs for three of the four days. After reading your situation, if it were me, I would not do the extra FPs. The reasons for us to get the extra FPs were 1) FOP and SDD tough to get, 2) doing 2 tier 1 FP in advance at Epcot, 3) and not having to rope drop. On your trip, you aren't going to do FOP or SDD. You have FEA already, so assuming you can do both TT and Soarin (motion sickness again?), you could do a FP for Soarin and single ride Test Track. Or, perhaps you want neither of those so will pick a different tier 1 at Epcot to go along with your extra FEA. Finally, you are avid RD'ers. I think I'd save the money for a nice meal (HDDR IS SO FUN!), a different event, souvenirs, or the fund for the next trip. Have a great time with your sister at WDW!
PS...Nonetheless, if you do decide to CLFP anyway, you will have the luxury of not having to be up at crack of dawn on 60 day mark fighting with everyone else/dealing with Stitch errors, etc. So, I can still see some benefit in booking the CLFP; however, not nearly as much as if you wanted more headline attractions.