So it finally happened. I found a fatal wound in my faithful old beater bike. The Bottom bracket mounting point has a split running the full width of the threading. Its solid and shows no sign of movement, and the bike still rides smooth as ever so I'm going to ride her until the BB fails. On top of this the front shock is so old its a pogo stick, the rear derailer mounting point is stripped so the derailler is riding on the wheel axle with a shortened chain to make up for the positioning. It all rides great, but once that bottom bracket goes it all over.
1) Source a new frame from somewhere: I have a source for a good second hand shock for $40 with a brand new v brake assembly on it. With a new frame (preferably second hand aluminium mtb) I would only need a longer chain, new bb, and transfer the rest of the parts. The gears are 21 speed shimano indexed and work great. The front has been modded with a 48t large chain ring and she rides super smooth even with 30kg of kid or stuff on the back. I think with $150-$200 worth of parts I could bring her back to life (and get the frame a little larger so it fits better)
2) Buy a new low-mid range bike and just transfer the rack/basket/computer/commuter tires etc to it. I think this would cost more like $400 but I'd end up with better gearing etc if I got the right bike. Thing is if I'm not careful at that sort of price I could also end up with something that rides inferior to what I have now.
This bike is my everyday ride to work/shopping/kid carrying I don't care if someone steals it bike so I don't want it be worth all that much, or look nice enough to steal.