LiFePo4 Slow charging 100 AH OK?
Generally charging cells slowly means they stay at high charge levels for very, very long, because they have internal leakage that increases with their voltage. Or they may even never reach completely full.

A completely full cell degrades much quicker.

However, LiFePO4 is a bit special, it deteriorates much less differentiated over state of charge. (It doesn't go bad three times as quick when completely full, like normal LiIon, only a bit faster). And it also is capable of handling levels of over charge, and has quite low internal leakage.

Now, of course, one LiFePO4 battery isn't the next, so I cannot tell you your stack's leakage currents. I would be surprised, however if they came close to dozens of mA, leave alone Ampere.

The only important thing that traditional Lithium Ion and LiFePO4 share is the wisdom in keeping cells balanced on voltage. So if you charge and discharge often and don't know for sure they will be completely topped-off cycles, it's wise to get an active balancer for the cells.

Just try it, if the last leg of the charging cycle doesn't take more than twice what you would expect based on linear maths, it's extremely likely it'll be fine.