Welsh phrase translation help please!

[SearchingforSleep]

I'm trying to write a card in Welsh - could anyone proof read for me please? Thank you!

Many, many congratulations on [name]'s safe arrival. Hope you are all doing well.

Llongyfarchiadau mawr, mawr ar cyrraedd yn ddiogel [name]. Gobeithio bod chi gyd yn gwneud da iawn.

This is from the BBC website:
Llongyfarchiadau ar enedigaeth eich plentyn / mab / merch.

• Congratulations on the birth of your child /son / daughter.

Hwyl fawr iawn!

I would put 'llongyfarchiadau ar enedigaeth baby's name' translating to congratulations on the birth of.
'Gobeithio fod pawb yn cadw yn iawn' is translation for hope everyone is keeping well, although I am north Wales welsh might be slightly different in south. Hth!

Hwyl fawr to me means goodbye!

Sorry last post, can't see op when replying on iPad! You can put llongyfarchiadau mawr if you want to say huge congrats!

Thanks so much to you both - very much appreciated. Diolch yn fawr!