Acceptable? There's really no rules or tartan police out there. There are a few restricted tartans out there...but if they're restricted, you won't be able to get your hands on them anyways...so don't worry about that.

The tartan of the A&SH is the government sett...more commonly known as the Black Watch Tartan. Black Watch is probably THE most well known and universal tartan worldwide...so if that's what you want to wear, go for it. The fact that, if asked, you can say that you are wearing it in honor of your grandfather's service in the A&SH...well that's just icing on the cake...but you certainly don't need to that fact to defend your choice or right to wear it.

Hope that helps. PS...there is a search function along the top bar in the forum. You've asked the same or similar question as about 50% of other new forum members. You may want to search and read some previous responses to get a better appreciation of the general opinions on tartan choice.