Google Photos is a solid start but set upload to Original quality and pre-clean the old drives with a basic duplicate finder so you don’t end up with near-duplicates or wrong dates. If you have Amazon Prime, Amazon Photos with Family Vault is an easy alternative that keeps full resolution and is parent-friendly. For the offline copy, keep one “Master Photos” folder on an external drive and use Time Machine or Windows File History (or a simple mirroring tool) to clone it to a second drive so you have two local copies plus the cloud.
Rule of thumb is every 3 months or sooner if the bristles splay or the indicator bristles fade and since frayed bristles clean less effectively and can irritate gums. If yours are wearing out fast, ease up on pressure and let the brush do the work; a pressure sensor or switching to a softer head can help. Store the head upright and uncapped to dry, and consider replacing a bit earlier after a cold or flu.