Through my experience homes of that square footage and the normal appliances like dryer, stove, oven, hot water heater etc that run on electric I would determine that 100amp service would suffice if the question was originally, "I presently have 100amp service and all equipment is in good condition; thinking about upgrading to 200amps-should I?"; however since all electrical equipment if far from even fair condition and the thought of all the extra power consuming devices/appliances that you already have plus what you are planning to have (even possibly) in the future it is my opinion that upgrading the entire service to 200amp is beneficial in this case and wise.
If the upgrade is within your budget I would do it all at the same time. Upgrade your service entrance cable from the tri-plex to the meter pan, be sure the new meter pan is rated at least to 200amp, replace the service entrance to the disconnect (main panel; which I would highly suggest you install; as mainly a safety and convenience factor). Install a SER cable from the main disconnect to the new panel (sub panel) and bang; you have a great new service that should last you a long time to come and you won't have to look at it again and say :help: then you can add any power consuming devices you want without thought (well almost not thought) in the future. The most important thing is securing that electric service so it is safe and functions efficiently.
The cost of a 200amp panel compared to a 100amp panel is not drastic. Most meter pans today are only rated at least 200amp so that won't matter, the extra cost of a disconnect is worth the money for convenience and safety. Explore your options with the sub panel (breaker panel). Remember that every load that is either 120/240 or 240 will require at least two full breaker spaces. All 120v circuits whether 15 or 20amp can be on tandems. I would also suggest that since the house sat for years in all kinds of weather that you also think about changing out all receptacles to new ones. That is probably something you can do as you have time. This will serve several purposes; one it will allow you to know what is in the boxes in the way of connections, back stabs should be now pig tailed jumpers. When putting in the new receptacles since this is your home and you are not paying yourself labor charges I would wire the receptacles in parralell instead of the standard series. Meaning the cable coming in and going out get wired nutted together (respectively by hot, neutral, ground etc), then with a jumper in the wire nut going to the receptacle under the screw. This way if that or any receptacle should fail in the future you will still have continuity past that receptacle to all devices down-line. When replacing any light switches etc I would take pictures first before removing the conductors for future reference in case you have difficulty hooking up the new switch.
An after thought; be careful determining the number of breaker spaces you will need. Since this will be a total upgrade or even a new panel many municipalities (and of course highly suggested) is that you have a permit and a final inspection. Depending on the AHJ (A.uthority H.aving J.urisdiction) meaning your town etc they may require since this is a complete new install that all circuits leading to bedrooms etc have AFCI protection at the panel. Depending on what code cycle they are working on it may require AFCIs in almost every room. If this is the case keep in mind that AFCI breakers take up an entire slot; there are not to my knowledge yet AFCI tandem breakers.