2 hours ago, kalani said:

Wahou. The visibility was not great but what amount of mantas!

Plancton --> "bad" visibilty... but Mantas

At Hanifaru the manta are present in october/november ... the weather is not the best

20 minutes ago, CaolIla said:

Plancton --> "bad" visibilty... but Mantas

At Hanifaru the manta are present in october/november ... the weather is not the best

Yes that is indeed the difficulty. It seems to me that the suggestion of looking at Bali might e a good one if timing for the Maldives is not good, the advantage being that there is a huge range of options and flights to get there. this website seems to suggest Nusa Penida might indeed be a good option for the OP.

https://www.zubludiving.com/articles/zublu-insights/manta-ray-seasons-in-indonesia

February + Bali hummm not the good season
I believe August is ok.

Rather than adding up distance, add up travel time including required stopovers etc. That may change your perspective on where is viable.

For a family with mixed abilities and non-divers. Been there, done that. Not a trek. Maldives. You can see sharks, rays and turtles etc. on quite a few house reefs. Mantas have cleaning stations and can be found reasonably reliable. Less expensive resorts with good house reefs inme Ellaidho in north Ari and Filitheyo in North Nilhando. Bon Chance.

2 hours ago, Christian K said:

Filitheyo in North Nilhando

I was 2 times at Filitheyo The Manta station is far from the island and not allways theyre.

Not sure this is a good destination for a family.. OK for snorkeling you can see some turtle and fishes

They resort have a pool and the restaurant wasn't bad... but my experience are 10 years ago... the things change.

1 hour ago, CaolIla said:

I was 2 times at Filitheyo The Manta station is far from the island and not allways theyre.

Not sure this is a good destination for a family.. OK for snorkeling you can see some turtle and fishes

They resort have a pool and the restaurant wasn't bad... but my experience are 10 years ago... the things change.

Was there with extended family and we had a very good time. Good for snorkeling to. No mantas there but eagle rays and sharks on the house reef. Was a few years ago tho, 2019.

Edited Monday at 08:16 PM1 day by Christian K

I worked on Digurah and yes wouldn't recommend it for snorkeling - main snorkeling event is really snorkeling with the whalesharks, but it's basically trying to keep-up with a swimming whaleshark (and they are fast), and not really suitable for kids.
To be honest, it's not something I enjoyed facilitating when i was was there (too much chasing, hectic, too many boats dropping people too close to the sharks), so I'm not the best person to sell this to you.
Diving is good with easy access to thilas like Kudara thila, and a manta cleaning station, quite a few grey reefs and sometimes the odd silvertip. Not much of a house reef or land access.

La Paz (where I've also worked) would have been a good choice for the California sea lions and also whalesharks later in the year etc, but it's far and you're off-season (Los islotes is closed during mating season in August), and yes, it's far.
As suggested, Magdalena bay is really in a category of its own, but check the season.

Palau is doable - especially combined with seakayak tours or stand up paddle, but most of Palau's main sites are not the best for snorkeling. Still a good option, but keep in mind that all the action is on the Rock islands, and there's not much in water action around Koror, and no real beach other than PPR's or artificial beaches.
I loved the diving when I was working there but have mixed feelings about snorkeling. But yes, you can see mantas snorkeling at German Channel or reef sharks in the Rock islands (there's been some feeding going on around one of the main resting areas on a specific island so lots of blacktips) or snorkel the dropoff or Cemetery / Paradise reef.

If you can drop the big-animals requirement (or lower it to reef sharks, turtles and cephalopods), you can find places with excellent snorkeling and diving. Land-based central Raja-Ampat for instance, or Komodo NP in Indonesia.
It's probably changed a lot but snorkeling around the Dampier peer house reefs used to be be incredible, as were some islands with resorts just outside the Komodo national park like Kanawa or Sebayur.
As others have suggested Bali is still a good option, with mantas on Penida, as is Bunaken if turtles and coral are enough.

Edited yesterday at 01:14 AM1 day by bghazzal

I would cross Curacao off the list, that is not a big animal destination. Lots of small life.