You can easily do 220 kms over two days on that bike, provided you are fit enough. Get a more comfortable seat and put on narrower road tires like you said. Also I would suggest putting on bar ends to give you another hand position - they are cheap. No reason to get another bike unless you want one, and if you do there are plenty of good road or touring bikes available for around $1000 that would be more than sufficient for this ride.