I'm really sorry that you've lost them, you weren't close but the love was there. It's always hard losing someone, it's so final and it brings up lots in your head. How are you doing?
For funerals I always ask the family and loved ones. Every family wants different things, some want relaxed and informal, some want elegant, some absolutely don't want black.
If there's no dress code I personally go for semi formal plain black. So black trousers, plain black top, black boots, bag and then a black blazer or cardigan. I keep jewellery minimal and silver.
I pack in my bag my usual things plus water, several packs tissues, protein bar, mints, clothing delinter and sewing kit. I don't want anyone having any additional stress if a button comes off or anything!
Do the family get on or could there be tension?