The 3G USB + Mikrotik draws about 10 watts, which can make the battery last up to 25 hours, given zero charge from the panels.
The trees you see are actually not affecting the panels as they are north facing and the shadow of them doesn't fall on the panels. Picking the location and orientation was important. Also, trees in the bush can be sorted out pronto with a bit of labour.
Given the 90 watts of the combined panels, which will still probably eke out at least 5-6 watts during terribly cloudy days, and low power usage at night due to not much traffic, I'd guess the system will probably last for at least a week, before choking.
After which, a secondary battery or tertiary battery will probably keep the thing alive for way longer.