Seal basement floor before tiling
Unless you truly fix the water intrusion, sealing the floor will not work. I would do a moisture transmission test in your 'wet season', after the repairs are done:
secure a foot square of plastic to the floor in several locations.  You should review the information here: Basement floor with lots of moisture. 

A moisture meter (this one has a masonry setting) for before, during and after readings, will give you a lot of information.

Porcelain tile will, in effect, seal the floor, since porcelain tile is impervious to water (&lt;= 0.5% water absorption).  Be sure to use portland cement based thinset (the dry kind, NOT a premixed mastic "thinset").