My grandma has shingles. I can't remember what I have read about chickenpox caught this way - is it as good a way as any to get exposed or does it predispose them to shingles later in life somehow? My kids are 19m, 5 and 7 if it matters.
My son had shingles when he was 6yo after having already had chicken pox at 3yo. His twin sister caught chicken pox from him a SECOND time.
(My dh also had CP twice)
It shouldn't affect your dc likelihood of getting shingles at all. I would do it if I were you-- but we're pretty well all set here now LOL. (My ds is more likely to get shingles later though--once you've had them there is a higher chance of recurrence. Which for you only affects your Grandma.)
Just this past winter, DS#1 (3yo), DS#2 (at 3 mo old), and I (31 yo) unintentionally got chickenpox from DH's shingles. (We had no idea it was shingles for days--who gets shingles at 34 yo? We thought he was having an allergic reaction to something. He probably touched the blisters then touched all of us)