Public transport advice for Aix to Hyeres to Cannes

The info you have seems wrong, unless the trains are not running on your dates.
You can take a direct bus or train from Aix to Marseille, followed by a direct train to Hyères. Or perhaps a bus from Aix to Toulon (Line 59) then train to Hyeres; it could be significantly faster.
There might also be buses from Toulon to Hyeres that could get you closer to your destination in Hyeres, whose train station is a bit far from the town center (still walkable).

For Hyeres to Cannes, I would take the train back to Toulon, then the train to Cannes.

balso, thanks for your help! I reviewed the SNCF website again after seeing your reply and I did see the options you mentioned. Unfortunately because my accomodations are somewhat far from the bus/train stations, it will be at least 3 changes for me (for example, the best itinerary on SNCF would be to walk 20 min to the train station, take the train from Aix to Marseille, then train from Marseille to Hyeres, then bus from Hyeres to accommodation near the Port Cros National Park, a total of 4 hours). Can I pay for the bus and train that day, or do you recommend reserving in advance?

The SNCF website does not always give the full picture!
Check out the "Zou Ma Région Sud" website. It has thorough bus timetables.

Aix bus station (gare routière) is 5 minutes more central than the train station. I would take the bus straight to Toulon.
In Toulon, you could take the train to Hyeres followed by buses, or you could take a taxi. They are readily available at the station. I reckon a trip to Giens Península (where I assume your accommodation is, given your description) would cost 60-75€ without excessive traffic, and there is also Uber. Maybe Bolt.

But you worry me when you say your accommodation is near Port Cros. Port Cros is an island. Are you staying on the island??

No reservations are needed, I do not think they are even possible.

balso, thanks for reminding me to check to make sure my accommodation is not on an island. The hotel description says it's "in Port Cros National Park" but it looks to be north of Giens Península. I plan on pre-booking my train rides through SNCF website ahead of time and have the Uber and SNCF apps on my phone just in case. Is there anything else you would recommend that I do to prepare for public transportation?

If you are interested in the bus from Aix to Toulon, you could pre-book on the "Zou région sud" website (not SNCF), but February is not peak season so I would not worry too much.

If you do not take the bus from Aix to Toulon, then the bus (or slower train) from Aix to Marseille & the train from Marseille to Hyères do not accept reservations (unless you take a TGV train but has it little added value, the regional trains are fine). You can still buy train tickets beforehand if that is easier for you.

For buses around Toulon & Hyères, the network is called Réseau Mistral. Those are city buses, no reservations possible.

If the bus timing does not work, you can find Uber at Hyères station, by the way. That would be a less-than-20€ ride to your destination.

As a recap, your options are:

1. Bus (line 50) or train from Aix to Marseille, train from Marseille to Hyères (often direct), local bus or Uber/taxi to your accommodation
2. Bus (ZOU line 59) from Aix to Toulon, then: A. taxi/Uber from Toulon, about 60€ (avoid at rush hour!!!) or B. train from Toulon to Hyères, then local bus or Uber/taxi as in option 1.

Personally, I would do 2A. or 2B.
2A. removes all the pain from the trip (outside of rush hour, traffic is abysmal in eastern Toulon), 2B. is the cheapest option of all and still faster or just as fast than going through Marseille.

From Hyères to St Raphael, you have to find your way back to Toulon station, and take a train there.