Then you're turning your 2 of 3 into a 3 of 3. Imaging one of the seeds is in a safe deposit box in another country.
May be I don't understand you but I agree with Charles-Tim here. The seeds are what the OP needs to take care.
, you can recover your funds when you have all 3 keys.
However, the point of using 2 of 3 multisig, is that you can recover your funds without the third private key. I didn't want to type a lot on mobile last night, luckily hosseinimr93 explained it nicely already:
Assuming you have seed phrases A, B and C, for generating your 2 of 3 multi-signature wallet and spending fund from that, you need:
Seed A, Seed B, MPK C
or
Seed B, Seed C, MPK A
or
Seed A, Seed C, MPK B
(MPK = master public key)
Didn't I say the same? But that's not my point. My point was one does not need to keep the Master Public key saved as they can find the keys when they try all three seeds one by one and each time they will get each Master Key. Then combine the master key and seed to recover the wallet. For a 2 of 3 wallet, two set is enough.