I sent 2 BTC (also from 2014) from MultiBit Classic to Electrum over 3 months ago. One went trough within hours. The second one (a child of the first one) was stuck and remained unconfirmed.
After 3 days I managed to get it trough within 2 hours or so using the
ViaBTC Transaction Accelerator. They do not have enough slots for everybody. The number of slots per hour are gone within a minute. The trick is to enter your Transaction ID within seconds after a new hour starts.
According to my knowledge moving BTC to a new client by simply sending them trough a regular transaction is even the best way to transfer them. Your BTC arrive in a wallet that has a seed. I haven't heard of any incomparability issues yet. If they really remain unconfirmed, they bounce back to you after a while. You won't loose them. I would recommend the highest fee possible in MultiBit Classic.
In Electrum 2.0, you cannot import private keys in a wallet that has a seed. You should sweep them instead. If you want to import private keys and not sweep them you need to create a special wallet that does not have a seed. For this, create a new wallet, select “restore”, and instead of typing your seed, type a list of private keys, or a list of addresses if you want to create a watching-only wallet.
Good luck!