Question for the mondern football collector

Hi there. My son is a huge Vikings fan. I want to buy him a couple of Adrian Peterson's cards, but don't know which cards of his are the better cards to collect. I only collect Hockey and Baseball cards and have no idea what is a fair price for Peterson's cards. I would like to get some of his rookie cards for my son, but don't know where to start. I looked on ebay, but wanted to get opinions on where to start. This isn't for future value, its just for my son (he is 6) with the hope he gets that collecting itch. Any help is much appreciated. Thanks in advance.
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Football
1973 Topps PSA 8+ (99.81%)
1976 Topps PSA 9+ (36.36%)
1977 Topps PSA 9+ (100%)
Baseball
1938 Goudey (56.25%)
1951 Topps Redbacks PSA 8 (100%)
1952 Bowman PSA 7+ (63.10%)
1953 Topps PSA 5+ (91.24%)
1973 Topps PSA 8+ (70.76%)
1985 Fleer PSA 10 (54.85%)