Perhaps "soillse ann mo cridhe".
In the context of "Brightness in my heart" what is needed (I feel) is more like : i - préposition (place)i - pronoms prépositionnels (ionam, ionat, ann, inti, ionainn, ionaibh, iontu)
Salut Hermeline,
Welcome to the forums.
I only speak a little Irish Gaelic (Gaeilge), and no Scottish Gaelic (Gàidhlig) at all, so I cannot be much help to you.
However I do wonder if petit1 is a native Scottish speaker ; since the word ann (adv) means there (in Irish at any rate), unsure where it fits in your sentence.
The English Scottish gaelic dictionaries give "ann".
http://www.dicts.info/dictionary.php?l1=English&l2=Scottish_Gaelic&word=in&Search=Rechercher
The Scottish Gaelic equivalents are listed (in that linked on-line dictionary) as follows :In the Irish version of in = i becomes in before vowels, combines with an to form sa before consonants and san before vowels ; combines with na to form 'sna
Source : My trusty Oxford (pocket) Irish dictionary.