Should I charge two four cell packs that I run parallel together? Do I just put a balancer on each pack?

The packs are both 4s 2650mah. Does this allow me to charge them at 5.3mah?

No, you need to charge them seperately. You can damage the cells charging them in parallel.

If they are lipo or li-ion packs then they can be charged in parallel (same as you use them)

i wouldn't if they were discharged to the different levels unless your balancing them both, with separate blancers at the same time to ensure equal voltages, then again with a 3rd inline charge balancer to ensure all voltages are equal while charging

the lug

Both are lipos and used in a truggy in parallel.

At what rate would I charge them?

You can charge them at double speed (current) compared to just one pack. If you use 2.5 amps then for two of them you can use 5 amps.

you can safely charge at 5 amps (just under 1C for both packs in parallel)