Hi,

Replication is more like a reporting solution, it gives you choice of tables ore even columns that needs to be replicated.

Mirroring can be considered as DR (I had a set up we implemeted Mirroring across datacenters) but it is costly either in terms of budget or performance.

(One advantage for mirroring is it give you capability for failback (role reversal))

I think best option for you is log shipping. You can build it over your existing backup plan. Considering the number of databases only thing you might need have a good plan for monitoring, failover and faiback.

In log shipping failback is possible but you need to create your on custom steps.