Help arranging/buying seats

I need help deciding on arranging seats and possibly buying a new one. dd1 is riding in an MA as her primary seat, and after reading about the MA crash test results, I want to change things.

dd1 5y7m, 36 pounds
dd2 3y5m, 31.5 pounds, 13.5 in shoulder height

I didn't get dd1's shoulder height, but she's just over the 2nd harness position from the top on the MA.

So right now they ride in my car 95% of the time- 04 Santa Fe. dd1 FF in MA, dd2 RF in TF.

DH's car is a 2 door 99 Civic. dd1 has the EFTA and ss2 has the original Triumph FF. They almost never ride in this car. We use the Santa Fe when we go out together on the weekends.

I'd like a spare seat in my mom's car, since she occasionally picks one or the other up from school. They have been riding in my mom's car more often than DHs.

I'm thinking my options are:
1. Switch dd2 to the MA RF and dd1 to the TF FF. I don't know about the RF leg room in the MA for dd2. Its a 33lb RF limit. Move the EFTA to my mom's car to be used for either dd. I'd leave the Triumph in DH's car for dd2, if we split up on weekends. We would need to move the EFTA if both dd's needed to ride in DHs car

2. Buy dd1 a Nautilus for my car. Leave dd2 RF in the TF. EFTA in my mom's car for either dd. The MA and the Triumph in DHs car. The MA would rarely be used, but I'm not sure how safe it is FF for dd1 at 36 pounds

Thanks for reading all of that

I'd love any opinions or any suggestions for other ideas, too.

Anyone have an opinion on RF dd2 in the MA at her age/size? I have read responses on someone else's thread about FF in the MA, but still looking for opinions.

I would just switch the seats in your car if you are concerned. My dd will be 3 in a couple weeks and she is rfing in a marathon. I feel she is very safe.