That is not much demand for power, but I don't know what is the best advice! You already have a generator, so you've got your lifeboat.
Your current converter makes a poor charger, so even though you've got the generator it will take FOREVER to charge your battery back up with it. So you could spend ~$200 on a new converter that is a 3-way smart charger and be able to recharge 1 or 2 batteries back up to 90% in a few hours time off of the generator.
Or you could spend upwards of $300 (total guess, but seems reasonable from my experience) for the 100W panel you mentioned, a decent charge controller, and nice fat wiring that would allow you to upgrade in the future without having to replace anything. This is assuming you are going to install it yourself. The solar will be putting juice back into your batteries at all times when the sun is shining, will be completely silent, and require no gas or maintenance. In storage, it will keep your batteries bursting full without having to disconnect them. In use, it might even keep your batteries charged enough to not need the generator. You don't need the batteries at 100% by the end of each day, you just don't want them much < 50% by the time you leave.
My vote is for the solar since you've already got your lifeboat.
