As an earlier poster mentioned, there's a good chance your "Gel" batteries are actually AGM-type. AGM's seem to be much more common. They're also a type of SLA (Sealed Lead Acid), but are closer to normal flooded batteries in terms of voltage setpoints and charging regime. Neither type should ever be equalized, or otherwise overcharged.
If your application allows for it, it might be better to set up two battery banks, with an A/B/Both paralleling switch in between, and charge them separately whenever possible. Paralleling both banks for discharge should be OK, so long as they're near the same state of charge.
Keeping them paralleled fulltime may work out OK, though, with careful choice of charging voltages to compromise between underchaging the flooding batts, and venting irreplacable water from your SLA's. Expect at least a small reduction in service life...