hello. the light festival thing is on next month and i'll probably go. Celtic park is not part of it, but it is paradise : ) Celtic park is a football stadium, not an actual park. The grass is pretty well kept though! It may be worth the trip up as there are other lovely gardens in glasgow but it may not be the best time of year to see them. Shopping here is great though if you fancied a garden/xmas shopping combo. I think there is a german xmas market on in glasgow that weekend too.
you could check it out on glasgow city council's website and you could check out greenbank gardens at the national trust scotland's site.
cheers, kerry