Ipad GEN 1 IOS 5.1.1

I have an old iPad probably the gen 1? I haven't used in years and kept it around when my children were babies to play games on. I found it the other day and it charged up and I set it up for them to play games on. Some of the old games are still on there and I connected my iTunes account to it. I keep trying to download abc mouse and other learning games and I have had to shut it off a few times trying to bc it freezes up. Will it be worth the trouble trying to update it or is that even an option with an older one like it? Thanks!