I have a similar spot in a score I'm finishing up. I didn't put the accent mark on the downbeat but it has the direction "let ring." The timpanist is not a native English speaker, so I added "(do not mute)" just to be super-redundantly clear.
Also I have him using harder mallets earlier, so that's why the direction for normal timpani mallet.
This isn't the best way to approach that. As a percussion player, I'd prefer that you don't use rests when you want something to ring or "vibrate." Simply tie that roll to the whole note and use, "l.v." which is the universal lingo for don't mute. Of course, you could keep the rests but it logistically, for site reading, would work better the other way.
As for the mallets. Usually, we use Soft, Med, or Hard to describe the type of mallets. Normal is typically Medium mallets so it's good to use a consistent form of description for the types of mallets, especially if you are doing stick changes throughout a piece.
Obviously you are communicating with your player which is great but if you publish this piece, you need to think about the masses versus just the individual player. Instructions like these can be seen as micro-managing, especially when there is a standard format for notating the instructions you've given. Also, they are cumbersome. Keep it simple and let the player make their own annotations in the part for their own performance decisions.
If you'd like a great percussion notation reference, I'd suggest checking out both "Music Notation by Gardner Reed" and "How to write for Percussion by Samuel Solomon." I wish I could give you an exact example (with pages) from the books but I recently just packed them up as I'm moving soon. Both are wonderful references to have nearby when notating your music.
Best,
Chris
PS: If you want to see really well done Timpani notation in the context of large scale works for ensembles, look up the music of David Manslanka. He passed away a few years ago but his site is still active and I believe you can access some PDF's of select scores (most are hand written, including the parts).