Buying tickets

My pops is turning 70 next month and my bro, sis and myself and all coming to town for the festivities. We’re planning on surprising him with tickets for the 4 of us for the June 5th day game against St. Louis and wanted to spring for some decent seats (thinking field-level, 1st base side, 10-30 rows back-ish). In y’all’s experience is it better to find tickets on Stub Hub or similar 3rd party site early or will I have better luck waiting until the game gets closer for the best prices. Any pearls appreciated. Thanks y’all.