Totally know what you mean 'play and learn'! I started with 3 tots the same age and went crazy! All 12/13 months at the start, and this is the first time I'm doing daycare after working in offices all my life! I'm down to 2 now...it does get a little lonely with no other adults around but I try to make play dates with neighbors/kids.
As for your 13 month old, is he/she still on 2 naps a day?